diff --git a/cmd/protoc-gen-openapi/generator/generator.go b/cmd/protoc-gen-openapi/generator/generator.go
index e548ab21..db30343f 100644
--- a/cmd/protoc-gen-openapi/generator/generator.go
+++ b/cmd/protoc-gen-openapi/generator/generator.go
@@ -133,11 +133,15 @@ func (g *OpenAPIv3Generator) buildDocumentV3() *v3.Document {
 	// While we have required schemas left to generate, go through the files again
 	// looking for the related message and adding them to the document if required.
 	for len(g.reflect.requiredSchemas) > 0 {
-		count := len(g.reflect.requiredSchemas)
 		for _, file := range g.plugin.Files {
 			g.addSchemasForMessagesToDocumentV3(d, file.Messages)
 		}
-		g.reflect.requiredSchemas = g.reflect.requiredSchemas[count:len(g.reflect.requiredSchemas)]
+		// clear the generated schemas
+		for schema := range g.reflect.requiredSchemas {
+			if contains(g.generatedSchemas, schema) {
+				delete(g.reflect.requiredSchemas, schema)
+			}
+		}
 	}
 
 	// If there is only 1 service, then use it's title for the
@@ -771,12 +775,14 @@ func (g *OpenAPIv3Generator) addPathsToDocumentV3(d *v3.Document, services []*pr
 	}
 }
 
-// addSchemaForMessageToDocumentV3 adds the schema to the document if required
+// addSchemaToDocumentV3 adds the schema to the document if required
 func (g *OpenAPIv3Generator) addSchemaToDocumentV3(d *v3.Document, schema *v3.NamedSchemaOrReference) {
-	if contains(g.generatedSchemas, schema.Name) {
-		return
+	// check if schema already exists in Schemas, instead of checking "generated"
+	for _, prop := range d.Components.Schemas.AdditionalProperties {
+		if prop.Name == schema.Name {
+			return
+		}
 	}
-	g.generatedSchemas = append(g.generatedSchemas, schema.Name)
 	d.Components.Schemas.AdditionalProperties = append(d.Components.Schemas.AdditionalProperties, schema)
 }
 
@@ -789,12 +795,25 @@ func (g *OpenAPIv3Generator) addSchemasForMessagesToDocumentV3(d *v3.Document, m
 		}
 
 		schemaName := g.reflect.formatMessageName(message.Desc)
+		fqSchemaName := g.reflect.formatPackageMessageName(message.Desc)
 
 		// Only generate this if we need it and haven't already generated it.
-		if !contains(g.reflect.requiredSchemas, schemaName) ||
-			contains(g.generatedSchemas, schemaName) {
+		requiredFQSchema, ok := g.reflect.requiredSchemas[schemaName]
+		if !ok {
+			continue
+		} else if requiredFQSchema != fqSchemaName {
+			// "schemaName" with same name is required, but it's not the actual
+			// schema with "fqSchemaName". Try to use the fully-qualified schema.
+			if _, ok = g.reflect.requiredSchemas[fqSchemaName]; !ok {
+				continue
+			}
+			// use fully-qualified name as schema name if there are same named messages
+			schemaName = fqSchemaName
+		}
+		if contains(g.generatedSchemas, schemaName) {
 			continue
 		}
+		g.generatedSchemas = append(g.generatedSchemas, schemaName)
 
 		typeName := g.reflect.fullMessageTypeName(message.Desc)
 		messageDescription := g.filterCommentString(message.Comments.Leading)
diff --git a/cmd/protoc-gen-openapi/generator/reflector.go b/cmd/protoc-gen-openapi/generator/reflector.go
index 31a0f930..5bce4522 100644
--- a/cmd/protoc-gen-openapi/generator/reflector.go
+++ b/cmd/protoc-gen-openapi/generator/reflector.go
@@ -33,7 +33,9 @@ const (
 type OpenAPIv3Reflector struct {
 	conf Configuration
 
-	requiredSchemas []string // Names of schemas which are used through references.
+	// Names of schemas which are used through references.
+	// map: schema name will be used actually -> fully-qualified schema name
+	requiredSchemas map[string]string
 }
 
 // NewOpenAPIv3Reflector creates a new reflector.
@@ -41,7 +43,7 @@ func NewOpenAPIv3Reflector(conf Configuration) *OpenAPIv3Reflector {
 	return &OpenAPIv3Reflector{
 		conf: conf,
 
-		requiredSchemas: make([]string, 0),
+		requiredSchemas: make(map[string]string, 0),
 	}
 }
 
@@ -86,6 +88,14 @@ func (r *OpenAPIv3Reflector) formatMessageName(message protoreflect.MessageDescr
 	return name
 }
 
+// formatPackageMessageName returns the fully-qualified name of a message.
+func (r *OpenAPIv3Reflector) formatPackageMessageName(message protoreflect.MessageDescriptor) string {
+	package_name := string(message.ParentFile().Package())
+	name := package_name + "." + r.getMessageName(message)
+
+	return name
+}
+
 func (r *OpenAPIv3Reflector) formatFieldName(field protoreflect.FieldDescriptor) string {
 	if *r.conf.Naming == "proto" {
 		return string(field.Name())
@@ -116,8 +126,15 @@ func (r *OpenAPIv3Reflector) responseContentForMessage(message protoreflect.Mess
 
 func (r *OpenAPIv3Reflector) schemaReferenceForMessage(message protoreflect.MessageDescriptor) string {
 	schemaName := r.formatMessageName(message)
-	if !contains(r.requiredSchemas, schemaName) {
-		r.requiredSchemas = append(r.requiredSchemas, schemaName)
+	fqSchemaName := r.formatPackageMessageName(message)
+	requiredFQSchema, ok := r.requiredSchemas[schemaName]
+	if !ok {
+		// new required, use schemaName
+		r.requiredSchemas[schemaName] = fqSchemaName
+	} else if requiredFQSchema != fqSchemaName {
+		// use the fully-qualified schema name as there are same named messages
+		schemaName = fqSchemaName
+		r.requiredSchemas[schemaName] = fqSchemaName
 	}
 	return "#/components/schemas/" + schemaName
 }