diff --git a/.changeset/cool-nails-provide.md b/.changeset/cool-nails-provide.md
new file mode 100644
index 0000000000..198cbe6496
--- /dev/null
+++ b/.changeset/cool-nails-provide.md
@@ -0,0 +1,5 @@
+---
+"@medusajs/core-flows": patch
+---
+
+fix(core-flows): guest email change to another guest email
diff --git a/integration-tests/modules/__tests__/cart/store/carts.spec.ts b/integration-tests/modules/__tests__/cart/store/carts.spec.ts
index fa00cbe0fb..2fd4aa6b2c 100644
--- a/integration-tests/modules/__tests__/cart/store/carts.spec.ts
+++ b/integration-tests/modules/__tests__/cart/store/carts.spec.ts
@@ -1730,6 +1730,157 @@ medusaIntegrationTestRunner({
           })
         })
 
+        it("should update the cart email from one guest account to another", async () => {
+          const guestsMainEmail = "guest.main@acme.com"
+          const guestsSecondaryEmail = "guest.secondary@acme.com"
+
+          const [guestMain, guestSecondary] =
+            await customerModule.createCustomers([
+              {
+                email: guestsMainEmail,
+                has_account: false,
+              },
+              {
+                email: guestsSecondaryEmail,
+                has_account: false,
+              },
+            ])
+
+          const cart = (
+            await api.post(
+              `/store/carts`,
+              {
+                currency_code: "usd",
+                email: guestsSecondaryEmail,
+                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
+
+          expect(cart.customer.id).toBe(guestSecondary.id)
+
+          // 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
+
+          expect(currentCartCustomer.id).toEqual(guestSecondary.id)
+          expect(currentCartCustomer.email).toEqual(guestSecondary.email)
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated",
+          })
+
+          // update the cart providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              email: guestsMainEmail,
+              metadata: {
+                test: "test updated 2, new customer",
+              },
+            },
+            storeHeaders
+          )
+
+          currentCart = await api.get(`/store/carts/${cart.id}`, storeHeaders)
+
+          expect(currentCart.data.cart.customer.id).toEqual(guestMain.id)
+          expect(currentCart.data.cart.email).toEqual(guestMain.email)
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated 2, new customer",
+          })
+        })
+
+        it("should persist customer on cart if updated with the same email", async () => {
+          const guestsMainEmail = "guest.main@acme.com"
+
+          const cart = (
+            await api.post(
+              `/store/carts`,
+              {
+                currency_code: "usd",
+                email: guestsMainEmail,
+                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 guestMain = cart.customer
+
+          // update the cart providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              email: guestsMainEmail, // update with the same mail
+              metadata: {
+                test: "test updated 2, same customer",
+              },
+            },
+            storeHeaders
+          )
+
+          let currentCart = await api.get(
+            `/store/carts/${cart.id}`,
+            storeHeaders
+          )
+
+          expect(currentCart.data.cart.customer.id).toEqual(guestMain.id)
+          expect(currentCart.data.cart.email).toEqual(guestMain.email)
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated 2, same customer",
+          })
+
+          // update the cart providing an email
+          await api.post(
+            `/store/carts/${cart.id}`,
+            {
+              email: guestsMainEmail, // update with the same mail
+              metadata: {
+                test: "test updated 3, same customer",
+              },
+            },
+            storeHeaders
+          )
+
+          currentCart = await api.get(`/store/carts/${cart.id}`, storeHeaders)
+
+          expect(currentCart.data.cart.customer.id).toEqual(guestMain.id)
+          expect(currentCart.data.cart.email).toEqual(guestMain.email)
+          expect(currentCart.data.cart.metadata).toEqual({
+            test: "test updated 3, same 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"
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 b6ed2100ec..cc075d89e7 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
@@ -39,12 +39,12 @@ interface StepCompensateInput {
 export const findOrCreateCustomerStepId = "find-or-create-customer"
 /**
  * This step finds or creates a customer based on the provided ID or email. It prioritizes finding the customer by ID, then by email.
- * 
+ *
  * The step creates a new customer either if:
- * 
+ *
  * - No customer is found with the provided ID and email;
  * - Or if it found the customer by ID but their email does not match the email in the input.
- * 
+ *
  * The step returns the details of the customer found or created, along with their email.
  */
 export const findOrCreateCustomerStep = createStep(
@@ -96,10 +96,14 @@ export const findOrCreateCustomerStep = createStep(
         })
       }
 
-      if (
-        !customer ||
-        (isDefined(data.email) && customer.email !== validatedEmail)
-      ) {
+      if (customer && customer.email !== validatedEmail) {
+        ;[customer] = await service.listCustomers({
+          email: validatedEmail,
+          has_account: false,
+        })
+      }
+
+      if (!customer) {
         customer = await service.createCustomers({ email: validatedEmail })
         customerWasCreated = true
       }