diff --git a/packages/region/integration-tests/__tests__/region-module.spec.ts b/packages/region/integration-tests/__tests__/region-module.spec.ts
index 261e6f3147..0ae7072c7d 100644
--- a/packages/region/integration-tests/__tests__/region-module.spec.ts
+++ b/packages/region/integration-tests/__tests__/region-module.spec.ts
@@ -196,6 +196,12 @@ moduleIntegrationTestRunner({
           countries: ["us", "ca"],
         })
 
+        const shouldNotBeChangedRegion = await service.create({
+          name: "Europe",
+          currency_code: "EUR",
+          countries: ["hr"],
+        })
+
         await service.update(createdRegion.id, {
           name: "Americas",
           currency_code: "MXN",
@@ -206,13 +212,26 @@ moduleIntegrationTestRunner({
           relations: ["countries"],
         })
 
+        const shouldNotBeChangedRegionAfter = await service.retrieve(
+          shouldNotBeChangedRegion.id,
+          {
+            relations: ["countries"],
+          }
+        )
+
         expect(latestRegion).toMatchObject({
           id: createdRegion.id,
           name: "Americas",
           currency_code: "mxn",
         })
 
-        expect(latestRegion.countries.map((c) => c.iso_2)).toEqual(["mx", "us"])
+        expect(
+          shouldNotBeChangedRegionAfter.countries.map((c) => c.iso_2)
+        ).toEqual(["hr"])
+
+        expect(latestRegion.countries.map((c) => c.iso_2)).toEqual(
+          expect.arrayContaining(["mx", "us"])
+        )
       })
 
       it("should update the region without affecting countries if countries are undefined", async () => {
@@ -340,12 +359,16 @@ moduleIntegrationTestRunner({
 
         await service.delete(createdRegion.id)
 
-        const resp = await service.create({
+        const newRegion = await service.create({
           name: "North America",
           currency_code: "USD",
           countries: ["us", "ca"],
         })
 
+        const resp = await service.retrieve(newRegion.id, {
+          relations: ["countries"],
+        })
+
         expect(resp.countries).toHaveLength(2)
       })
     })
diff --git a/packages/region/src/services/region-module.ts b/packages/region/src/services/region-module.ts
index 6e8140b1ae..f387fcbfa6 100644
--- a/packages/region/src/services/region-module.ts
+++ b/packages/region/src/services/region-module.ts
@@ -101,25 +101,36 @@ export default class RegionModuleService<
   ): Promise<Region[]> {
     let normalizedInput = RegionModuleService.normalizeInput(data)
 
-    const validations = [
-      this.validateCountries(
-        normalizedInput.map((r) => r.countries ?? []).flat(),
-        sharedContext
-      ),
-    ] as const
-
-    // Assign the full country object so the ORM updates the relationship
-    const [dbCountries] = await promiseAll(validations)
-    const dbCountriesMap = new Map(dbCountries.map((d) => [d.iso_2, d]))
     let normalizedDbRegions = normalizedInput.map((region) =>
       removeUndefined({
         ...region,
-        countries: region.countries?.map((c) => dbCountriesMap.get(c)),
+        countries: undefined,
       })
     )
 
-    // Create the regions and update the country region_id
-    return await this.regionService_.create(normalizedDbRegions, sharedContext)
+    const result = await this.regionService_.create(
+      normalizedDbRegions,
+      sharedContext
+    )
+
+    if (data.some((input) => input.countries?.length)) {
+      await this.validateCountries(
+        normalizedInput.map((r) => r.countries ?? []).flat(),
+        sharedContext
+      )
+
+      await this.countryService_.update(
+        normalizedInput.map((region, i) => ({
+          selector: { iso_2: region.countries },
+          data: {
+            region_id: result[i].id,
+          },
+        })),
+        sharedContext
+      )
+    }
+
+    return result
   }
 
   async upsert(
@@ -213,6 +224,13 @@ export default class RegionModuleService<
       .map((region) => region.id)
       .flat()
 
+    let normalizedDbRegions = normalizedInput.map((region) =>
+      removeUndefined({
+        ...region,
+        countries: undefined, // -> delete countries if passed because we want to do update "manually"
+      })
+    )
+
     if (regionsWithCountryUpdate.length) {
       await this.countryService_.update(
         {
@@ -223,24 +241,22 @@ export default class RegionModuleService<
         },
         sharedContext
       )
-    }
 
-    const validations = [
-      this.validateCountries(
+      await this.validateCountries(
         normalizedInput.map((d) => d.countries ?? []).flat(),
         sharedContext
-      ),
-    ] as const
+      )
 
-    // Assign the full country object so the ORM updates the relationship
-    const [dbCountries] = await promiseAll(validations)
-    const dbCountriesMap = new Map(dbCountries.map((d) => [d.iso_2, d]))
-    let normalizedDbRegions = normalizedInput.map((region) =>
-      removeUndefined({
-        ...region,
-        countries: region.countries?.map((c) => dbCountriesMap.get(c)),
-      })
-    )
+      await this.countryService_.update(
+        normalizedInput.map((region) => ({
+          selector: { iso_2: region.countries },
+          data: {
+            region_id: region.id,
+          },
+        })),
+        sharedContext
+      )
+    }
 
     return await this.regionService_.update(normalizedDbRegions, sharedContext)
   }
@@ -256,6 +272,14 @@ export default class RegionModuleService<
     )
   }
 
+  /**
+   * Validate that countries can be assigned to a region.
+   *
+   * NOTE: this method relies on countries of the regions that we are assigning to need to be unassigned first.
+   * @param countries
+   * @param sharedContext
+   * @private
+   */
   private async validateCountries(
     countries: string[] | undefined,
     sharedContext: Context