diff --git a/.changeset/bright-bees-decide.md b/.changeset/bright-bees-decide.md
new file mode 100644
index 0000000000..b28724aaf4
--- /dev/null
+++ b/.changeset/bright-bees-decide.md
@@ -0,0 +1,5 @@
+---
+"@medusajs/core-flows": patch
+---
+
+Keep customer when updating cart
diff --git a/integration-tests/modules/__tests__/cart/store/carts.spec.ts b/integration-tests/modules/__tests__/cart/store/carts.spec.ts
index 5777991203..e40873c772 100644
--- a/integration-tests/modules/__tests__/cart/store/carts.spec.ts
+++ b/integration-tests/modules/__tests__/cart/store/carts.spec.ts
@@ -1882,6 +1882,192 @@ medusaIntegrationTestRunner({
           })
         })
 
+        it("should create another guest customer and update the cart email when an different email is provided", async () => {
+          const cart = (
+            await api.post(
+              `/store/carts`,
+              {
+                currency_code: "usd",
+                email: "tony@stark-industries.com",
+                shipping_address: {
+                  address_1: "test address 1",
+                  address_2: "test address 2",
+                  city: "ny",
+                  country_code: "us",
+                  province: "ny",
+                  postal_code: "94016",
+                },
+                sales_channel_id: salesChannel.id,
+              },
+              storeHeaders
+            )
+          ).data.cart
+
+          const originalCartCustomer = cart.customer
+
+          // update the cart without providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              metadata: {
+                test: "test updated",
+              },
+            },
+            storeHeaders
+          )
+
+          let currentCart = await api.get(
+            `/store/carts/${cart.id}`,
+            storeHeaders
+          )
+          let currentCartCustomer = currentCart.data.cart.customer
+
+          let customerData = (
+            await api.get(
+              `/admin/customers/${currentCart.data.cart.customer_id}`,
+              adminHeaders
+            )
+          ).data.customer
+
+          expect(currentCartCustomer).toEqual(originalCartCustomer)
+          expect(customerData.email).toEqual(currentCart.data.cart.email)
+          expect(currentCart.data.cart.email).toEqual(
+            "tony@stark-industries.com"
+          )
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated",
+          })
+
+          // update the cart providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              email: "foo@bar.com",
+              metadata: {
+                test: "test updated 2, new customer",
+              },
+            },
+            storeHeaders
+          )
+
+          currentCart = await api.get(`/store/carts/${cart.id}`, storeHeaders)
+
+          customerData = (
+            await api.get(
+              `/admin/customers/${currentCart.data.cart.customer_id}`,
+              adminHeaders
+            )
+          ).data.customer
+
+          currentCartCustomer = currentCart.data.cart.customer
+
+          expect(currentCartCustomer).not.toEqual(originalCartCustomer)
+          expect(currentCart.data.cart.customer_id).not.toEqual(
+            originalCartCustomer.id
+          )
+          expect(customerData.email).toEqual(currentCart.data.cart.email)
+          expect(currentCart.data.cart.email).toEqual("foo@bar.com")
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated 2, new customer",
+          })
+        })
+
+        it("should keep the same customer when updating the customer cart and update Cart's email if provided", async () => {
+          // create a customer
+          const mainEmail = "jhon.doe@acme.com"
+          await customerModule.createCustomers({
+            email: mainEmail,
+            has_account: true,
+          })
+
+          const cart = (
+            await api.post(
+              `/store/carts`,
+              {
+                currency_code: "usd",
+                email: mainEmail,
+                shipping_address: {
+                  address_1: "test address 1",
+                  address_2: "test address 2",
+                  city: "ny",
+                  country_code: "us",
+                  province: "ny",
+                  postal_code: "94016",
+                },
+                sales_channel_id: salesChannel.id,
+              },
+              storeHeaders
+            )
+          ).data.cart
+
+          const originalCartCustomer = cart.customer
+
+          // update the cart without providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              metadata: {
+                test: "test updated",
+              },
+            },
+            storeHeaders
+          )
+
+          let currentCart = await api.get(
+            `/store/carts/${cart.id}`,
+            storeHeaders
+          )
+          let currentCartCustomer = currentCart.data.cart.customer
+
+          let customerData = (
+            await api.get(
+              `/admin/customers/${currentCart.data.cart.customer_id}`,
+              adminHeaders
+            )
+          ).data.customer
+
+          expect(currentCartCustomer).toEqual(originalCartCustomer)
+          expect(customerData.email).toEqual(currentCart.data.cart.email)
+          expect(currentCart.data.cart.email).toEqual(mainEmail)
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated",
+          })
+
+          // update the cart providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              email: "foo@bar.com",
+              metadata: {
+                test: "test updated 2, new customer",
+              },
+            },
+            storeHeaders
+          )
+
+          currentCart = await api.get(`/store/carts/${cart.id}`, storeHeaders)
+
+          customerData = (
+            await api.get(
+              `/admin/customers/${currentCart.data.cart.customer_id}`,
+              adminHeaders
+            )
+          ).data.customer
+
+          currentCartCustomer = currentCart.data.cart.customer
+
+          expect(currentCartCustomer).toEqual(originalCartCustomer)
+          expect(currentCart.data.cart.customer_id).toEqual(
+            originalCartCustomer.id
+          )
+          expect(customerData.email).not.toEqual(currentCart.data.cart.email)
+          expect(customerData.email).toEqual(mainEmail)
+          expect(currentCart.data.cart.email).toEqual("foo@bar.com")
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated 2, new customer",
+          })
+        })
+
         it("should return order when cart is already completed", async () => {
           const cart = (
             await api.post(
diff --git a/packages/core/core-flows/src/cart/steps/find-or-create-customer.ts b/packages/core/core-flows/src/cart/steps/find-or-create-customer.ts
index eead9681f9..3a651d9038 100644
--- a/packages/core/core-flows/src/cart/steps/find-or-create-customer.ts
+++ b/packages/core/core-flows/src/cart/steps/find-or-create-customer.ts
@@ -1,6 +1,6 @@
 import { CustomerDTO, ICustomerModuleService } from "@medusajs/framework/types"
-import { Modules, validateEmail } from "@medusajs/framework/utils"
-import { StepResponse, createStep } from "@medusajs/framework/workflows-sdk"
+import { isDefined, Modules, validateEmail } from "@medusajs/framework/utils"
+import { createStep, StepResponse } from "@medusajs/framework/workflows-sdk"
 
 export interface FindOrCreateCustomerStepInput {
   customerId?: string | null
@@ -21,20 +21,20 @@ export const findOrCreateCustomerStepId = "find-or-create-customer"
 /**
  * This step either finds a customer matching the specified ID, or finds / create a customer
  * matching the specified email. If both ID and email are provided, ID takes precedence.
+ * If the customer is a guest, the email is updated to the provided email.
  */
 export const findOrCreateCustomerStep = createStep(
   findOrCreateCustomerStepId,
   async (data: FindOrCreateCustomerStepInput, { container }) => {
-    if (
-      typeof data.customerId === undefined &&
-      typeof data.email === undefined
-    ) {
+    if (!isDefined(data.customerId) && !isDefined(data.email)) {
       return new StepResponse(
         {
           customer: undefined,
           email: undefined,
         },
-        { customerWasCreated: false }
+        {
+          customerWasCreated: false,
+        }
       )
     }
 
@@ -44,37 +44,50 @@ export const findOrCreateCustomerStep = createStep(
       customer: null,
       email: null,
     }
+    let originalCustomer: CustomerDTO | null = null
     let customerWasCreated = false
 
     if (data.customerId) {
-      const customer = await service.retrieveCustomer(data.customerId)
-      customerData.customer = customer
-      customerData.email = customer.email
-
-      return new StepResponse(customerData, {
-        customerWasCreated,
-      })
+      originalCustomer = await service.retrieveCustomer(data.customerId)
+      customerData.customer = originalCustomer
+      customerData.email = originalCustomer.email
     }
 
     if (data.email) {
-      const validatedEmail = validateEmail(data.email)
+      const validatedEmail = (data.email && validateEmail(data.email)) as string
 
-      let [customer] = await service.listCustomers({
-        email: validatedEmail,
-        has_account: false,
-      })
+      let [customer] = originalCustomer
+        ? [originalCustomer]
+        : await service.listCustomers({
+            email: validatedEmail,
+          })
 
-      if (!customer) {
+      // if NOT a guest customer, return it
+      if (customer?.has_account) {
+        customerData.customer = customer
+        customerData.email = customer.email
+
+        return new StepResponse(customerData, {
+          customerWasCreated,
+        })
+      }
+
+      if (
+        !customer ||
+        (isDefined(data.email) && customer.email !== validatedEmail)
+      ) {
         customer = await service.createCustomers({ email: validatedEmail })
         customerWasCreated = true
       }
 
+      originalCustomer = customer
+
       customerData.customer = customer
       customerData.email = customer.email
     }
 
     return new StepResponse(customerData, {
-      customer: customerData.customer,
+      customer: originalCustomer,
       customerWasCreated,
     })
   },
diff --git a/packages/core/core-flows/src/cart/workflows/update-cart.ts b/packages/core/core-flows/src/cart/workflows/update-cart.ts
index 5318d40408..9114ed6f57 100644
--- a/packages/core/core-flows/src/cart/workflows/update-cart.ts
+++ b/packages/core/core-flows/src/cart/workflows/update-cart.ts
@@ -34,18 +34,32 @@ export const updateCartWorkflow = createWorkflow(
     const cartToUpdate = useRemoteQueryStep({
       entry_point: "cart",
       variables: { id: input.id },
-      fields: ["id", "shipping_address.*", "region.*", "region.countries.*"],
+      fields: [
+        "id",
+        "email",
+        "customer_id",
+        "shipping_address.*",
+        "region.*",
+        "region.countries.*",
+      ],
       list: false,
       throw_if_key_not_found: true,
     }).config({ name: "get-cart" })
 
-    const [salesChannel, customerData] = parallelize(
+    const customerDataInput = transform({ input, cartToUpdate }, (data) => {
+      return {
+        customer_id: data.cartToUpdate.customer_id,
+        email: data.input.email ?? data.cartToUpdate.email,
+      }
+    })
+
+    const [salesChannel, customer] = parallelize(
       findSalesChannelStep({
         salesChannelId: input.sales_channel_id,
       }),
       findOrCreateCustomerStep({
-        customerId: input.customer_id,
-        email: input.email,
+        customerId: customerDataInput.customer_id,
+        email: customerDataInput.email,
       })
     )
 
@@ -66,7 +80,13 @@ export const updateCartWorkflow = createWorkflow(
     })
 
     const cartInput = transform(
-      { input, region, customerData, salesChannel, cartToUpdate },
+      {
+        input,
+        region,
+        customer,
+        salesChannel,
+        cartToUpdate,
+      },
       (data) => {
         const {
           promo_codes,
@@ -116,13 +136,16 @@ export const updateCartWorkflow = createWorkflow(
           }
         }
 
-        if (
-          isDefined(updateCartData.customer_id) ||
-          isDefined(updateCartData.email)
-        ) {
-          data_.customer_id = data.customerData.customer?.id || null
-          data_.email =
-            data.input?.email ?? (data.customerData.customer?.email || null)
+        if (isDefined(updateCartData.email) && data.customer?.customer) {
+          const currentCustomer = data.customer.customer!
+          data_.customer_id = currentCustomer.id
+
+          // registered customers can update the cart email
+          if (currentCustomer.has_account) {
+            data_.email = updateCartData.email
+          } else {
+            data_.email = data.customer.email
+          }
         }
 
         if (isDefined(updateCartData.sales_channel_id)) {
@@ -133,6 +156,7 @@ export const updateCartWorkflow = createWorkflow(
       }
     )
 
+    /*
     when({ cartInput }, ({ cartInput }) => {
       return isDefined(cartInput.customer_id) || isDefined(cartInput.email)
     }).then(() => {
@@ -141,6 +165,7 @@ export const updateCartWorkflow = createWorkflow(
         data: { id: input.id },
       }).config({ name: "emit-customer-updated" })
     })
+    */
 
     when({ input, cartToUpdate }, ({ input, cartToUpdate }) => {
       return (