diff --git a/psl/parser-database/src/attributes.rs b/psl/parser-database/src/attributes.rs
index ac5a0276d450..6e34b6e41ca1 100644
--- a/psl/parser-database/src/attributes.rs
+++ b/psl/parser-database/src/attributes.rs
@@ -155,7 +155,7 @@ fn resolve_model_attributes<'db>(model_id: ast::ModelId, ast_model: &'db ast::Mo
 
     // @@map
     if ctx.visit_optional_single_attr("map") {
-        map::model(&mut model_attributes, model_id, ctx);
+        map::model(&mut model_attributes, ctx);
         ctx.validate_visited_arguments();
     }
 
diff --git a/psl/parser-database/src/attributes/map.rs b/psl/parser-database/src/attributes/map.rs
index 5aed9dcff68e..28b9c4444f55 100644
--- a/psl/parser-database/src/attributes/map.rs
+++ b/psl/parser-database/src/attributes/map.rs
@@ -6,31 +6,13 @@ use crate::{
     DatamodelError, StringId,
 };
 
-pub(super) fn model(model_attributes: &mut ModelAttributes, model_id: ast::ModelId, ctx: &mut Context<'_>) {
+pub(super) fn model(model_attributes: &mut ModelAttributes, ctx: &mut Context<'_>) {
     let mapped_name = match visit_map_attribute(ctx) {
         Some(name) => name,
         None => return,
     };
 
     model_attributes.mapped_name = Some(mapped_name);
-
-    if let Some(existing_model_id) = ctx.mapped_model_names.insert(mapped_name, model_id) {
-        let existing_model_name = ctx.ast[existing_model_id].name();
-        ctx.push_error(DatamodelError::new_duplicate_model_database_name_error(
-            &ctx[mapped_name],
-            existing_model_name,
-            ctx.ast[model_id].span(),
-        ));
-    }
-
-    if let Some(existing_model_id) = ctx.names.tops.get(&mapped_name).and_then(|id| id.as_model_id()) {
-        let existing_model_name = ctx.ast[existing_model_id].name();
-        ctx.push_error(DatamodelError::new_duplicate_model_database_name_error(
-            &ctx[mapped_name],
-            existing_model_name,
-            ctx.current_attribute().span,
-        ));
-    }
 }
 
 pub(super) fn scalar_field(
diff --git a/psl/parser-database/src/context.rs b/psl/parser-database/src/context.rs
index aa37cca7bb6d..54c06ddd9a42 100644
--- a/psl/parser-database/src/context.rs
+++ b/psl/parser-database/src/context.rs
@@ -30,7 +30,6 @@ pub(crate) struct Context<'db> {
     attributes: AttributesValidationState, // state machine for attribute validation
 
     // @map'ed names indexes. These are not in the db because they are only used for validation.
-    pub(super) mapped_model_names: HashMap<StringId, ast::ModelId>,
     pub(super) mapped_model_scalar_field_names: HashMap<(ast::ModelId, StringId), ast::FieldId>,
     pub(super) mapped_composite_type_names: HashMap<(ast::CompositeTypeId, StringId), ast::FieldId>,
     pub(super) mapped_enum_names: HashMap<StringId, ast::EnumId>,
@@ -55,7 +54,6 @@ impl<'db> Context<'db> {
             diagnostics,
             attributes: AttributesValidationState::default(),
 
-            mapped_model_names: Default::default(),
             mapped_model_scalar_field_names: Default::default(),
             mapped_enum_names: Default::default(),
             mapped_enum_value_names: Default::default(),
diff --git a/psl/parser-database/src/lib.rs b/psl/parser-database/src/lib.rs
index 4fde9cff3c96..c9575b667d47 100644
--- a/psl/parser-database/src/lib.rs
+++ b/psl/parser-database/src/lib.rs
@@ -140,7 +140,7 @@ impl ParserDatabase {
         &self.ast
     }
 
-    /// The total number of models.
+    /// The total number of models. This is O(1).
     pub fn models_count(&self) -> usize {
         self.types.model_attributes.len()
     }
diff --git a/psl/psl-core/src/validate/validation_pipeline/validations.rs b/psl/psl-core/src/validate/validation_pipeline/validations.rs
index f8fd19e383c3..22474016202b 100644
--- a/psl/psl-core/src/validate/validation_pipeline/validations.rs
+++ b/psl/psl-core/src/validate/validation_pipeline/validations.rs
@@ -36,10 +36,12 @@ pub(super) fn validate(ctx: &mut Context<'_>) {
         }
     }
 
-    // Model validations
     ctx.connector
         .validate_scalar_field_unknown_default_functions(ctx.db, ctx.diagnostics);
 
+    // Model validations
+    models::database_name_clashes(ctx);
+
     for model in db.walk_models() {
         models::has_a_strict_unique_criteria(model, ctx);
         models::has_a_unique_primary_key_name(model, &names, ctx);
diff --git a/psl/psl-core/src/validate/validation_pipeline/validations/models.rs b/psl/psl-core/src/validate/validation_pipeline/validations/models.rs
index 78b228152899..74dbb5d3aebf 100644
--- a/psl/psl-core/src/validate/validation_pipeline/validations/models.rs
+++ b/psl/psl-core/src/validate/validation_pipeline/validations/models.rs
@@ -1,13 +1,14 @@
 use super::database_name::validate_db_name;
 use crate::{
+    ast,
     common::preview_features::PreviewFeature,
     datamodel_connector::{walker_ext_traits::*, ConnectorCapability},
     diagnostics::DatamodelError,
-    parser_database::ast::WithSpan,
+    parser_database::ast::{WithName, WithSpan},
     validate::validation_pipeline::context::Context,
 };
 use parser_database::walkers::{ModelWalker, PrimaryKeyWalker};
-use std::borrow::Cow;
+use std::{borrow::Cow, collections::HashMap};
 
 /// A model must have either a primary key, or a unique criteria
 /// with no optional, commented-out or unsupported fields.
@@ -298,3 +299,46 @@ pub(super) fn schema_attribute(model: ModelWalker<'_>, ctx: &mut Context<'_>) {
         _ => (),
     }
 }
+
+pub(super) fn database_name_clashes(ctx: &mut Context<'_>) {
+    // (schema_name, model_database_name) -> ModelId
+    let mut database_names: HashMap<(Option<&str>, &str), ast::ModelId> = HashMap::with_capacity(ctx.db.models_count());
+
+    for model in ctx.db.walk_models() {
+        let key = (model.schema().map(|(name, _)| name), model.database_name());
+        match database_names.insert(key, model.model_id()) {
+            // Two branches because we want to put the error on the @@map attribute, and it can be
+            // on either model.
+            Some(existing) if model.mapped_name().is_some() => {
+                let existing_model_name = &ctx.db.ast()[existing].name();
+                let attribute = model
+                    .ast_model()
+                    .attributes
+                    .iter()
+                    .find(|attr| attr.name() == "map")
+                    .unwrap();
+
+                ctx.push_error(DatamodelError::new_duplicate_model_database_name_error(
+                    model.database_name(),
+                    existing_model_name,
+                    attribute.span(),
+                ));
+            }
+            Some(existing) => {
+                let existing_model = &ctx.db.ast()[existing];
+                let attribute = existing_model
+                    .attributes
+                    .iter()
+                    .find(|attr| attr.name() == "map")
+                    .unwrap();
+
+                ctx.push_error(DatamodelError::new_duplicate_model_database_name_error(
+                    model.database_name(),
+                    model.name(),
+                    attribute.span(),
+                ));
+            }
+            None => (),
+        }
+    }
+}
diff --git a/psl/psl/tests/validation/attributes/map/duplicate_models_with_map_on_both_sides.prisma b/psl/psl/tests/validation/attributes/map/duplicate_models_with_map_on_both_sides.prisma
new file mode 100644
index 000000000000..6ee838e2d32b
--- /dev/null
+++ b/psl/psl/tests/validation/attributes/map/duplicate_models_with_map_on_both_sides.prisma
@@ -0,0 +1,23 @@
+datasource mydb {
+    provider = "sqlite"
+    url = env("TEST_DB_URL")
+}
+
+model Dog {
+  id Int @id
+
+  @@map("pets")
+}
+
+model Cat {
+  id Int @id
+
+  @@map("pets")
+}
+
+// error: The model with database name "pets" could not be defined because another model with this name exists: "Dog"
+//   -->  schema.prisma:15
+//    | 
+// 14 | 
+// 15 |   @@map("pets")
+//    | 
diff --git a/psl/psl/tests/validation/attributes/schema/tables_in_different_schemas_with_same_mapped_name.prisma b/psl/psl/tests/validation/attributes/schema/tables_in_different_schemas_with_same_mapped_name.prisma
new file mode 100644
index 000000000000..a50b66a4c545
--- /dev/null
+++ b/psl/psl/tests/validation/attributes/schema/tables_in_different_schemas_with_same_mapped_name.prisma
@@ -0,0 +1,30 @@
+// issue: https://github.com/prisma/prisma/issues/15009
+
+generator client {
+  provider        = "prisma-client-js"
+  previewFeatures = ["multiSchema"]
+}
+
+datasource db {
+  provider = "postgresql"
+  url      = env("TEST_DATABASE_URL")
+  schemas  = ["base", "transactional"]
+}
+
+model User {
+  id    String @id
+  email String
+  posts Post[]
+
+  @@map("some_table")
+  @@schema("base")
+}
+
+model Post {
+  title    String
+  authorId String @unique
+  author   User?  @relation(fields: [authorId], references: [id])
+
+  @@map("some_table")
+  @@schema("transactional")
+}
diff --git a/psl/psl/tests/validation/attributes/schema/tables_in_same_schema_with_same_mapped_name.prisma b/psl/psl/tests/validation/attributes/schema/tables_in_same_schema_with_same_mapped_name.prisma
new file mode 100644
index 000000000000..f1c77a8e4f6f
--- /dev/null
+++ b/psl/psl/tests/validation/attributes/schema/tables_in_same_schema_with_same_mapped_name.prisma
@@ -0,0 +1,32 @@
+datasource mydb {
+  provider = "sqlserver"
+  url = env("TEST_DB_URL")
+  schemas  = ["base", "transactional"]
+}
+
+generator client {
+  provider        = "prisma-client-js"
+  previewFeatures = ["multiSchema"]
+}
+
+
+model Dog {
+  id Int @id
+
+  @@map("pets")
+  @@schema("base")
+}
+
+model Cat {
+  id Int @id(map: "cat_pets_pkey")
+
+  @@map("pets")
+  @@schema("base")
+}
+
+// error: The model with database name "pets" could not be defined because another model with this name exists: "Dog"
+//   -->  schema.prisma:23
+//    | 
+// 22 | 
+// 23 |   @@map("pets")
+//    |