diff --git a/internal/query/projection/projection.go b/internal/query/projection/projection.go
index e89530bf0d..b8dac72b9a 100644
--- a/internal/query/projection/projection.go
+++ b/internal/query/projection/projection.go
@@ -209,10 +209,18 @@ func Init(ctx context.Context) error {
 	return nil
 }
 
-func Start(ctx context.Context) {
+func Start(ctx context.Context) error {
+	projectionTableMap := make(map[string]bool, len(projections))
 	for _, projection := range projections {
+		table := projection.String()
+		if projectionTableMap[table] {
+			return fmt.Errorf("projeciton for %s already added", table)
+		}
+		projectionTableMap[table] = true
+
 		projection.Start(ctx)
 	}
+	return nil
 }
 
 func ProjectInstance(ctx context.Context) error {
diff --git a/internal/query/projection/projection_mock.go b/internal/query/projection/projection_mock.go
new file mode 100644
index 0000000000..6ba50082ae
--- /dev/null
+++ b/internal/query/projection/projection_mock.go
@@ -0,0 +1,130 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: projection.go
+//
+// Generated by this command:
+//
+//	mockgen -source projection.go -destination ./projection_mock.go -package projection
+//
+
+// Package projection is a generated GoMock package.
+package projection
+
+import (
+	context "context"
+	reflect "reflect"
+
+	eventstore "github.com/zitadel/zitadel/internal/eventstore"
+	handler "github.com/zitadel/zitadel/internal/eventstore/handler/v2"
+	gomock "go.uber.org/mock/gomock"
+)
+
+// Mockprojection is a mock of projection interface.
+type Mockprojection struct {
+	ctrl     *gomock.Controller
+	recorder *MockprojectionMockRecorder
+}
+
+// MockprojectionMockRecorder is the mock recorder for Mockprojection.
+type MockprojectionMockRecorder struct {
+	mock *Mockprojection
+}
+
+// NewMockprojection creates a new mock instance.
+func NewMockprojection(ctrl *gomock.Controller) *Mockprojection {
+	mock := &Mockprojection{ctrl: ctrl}
+	mock.recorder = &MockprojectionMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *Mockprojection) EXPECT() *MockprojectionMockRecorder {
+	return m.recorder
+}
+
+// Execute mocks base method.
+func (m *Mockprojection) Execute(ctx context.Context, startedEvent eventstore.Event) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Execute", ctx, startedEvent)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Execute indicates an expected call of Execute.
+func (mr *MockprojectionMockRecorder) Execute(ctx, startedEvent any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Execute", reflect.TypeOf((*Mockprojection)(nil).Execute), ctx, startedEvent)
+}
+
+// Init mocks base method.
+func (m *Mockprojection) Init(ctx context.Context) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Init", ctx)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Init indicates an expected call of Init.
+func (mr *MockprojectionMockRecorder) Init(ctx any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Init", reflect.TypeOf((*Mockprojection)(nil).Init), ctx)
+}
+
+// ProjectionName mocks base method.
+func (m *Mockprojection) ProjectionName() string {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ProjectionName")
+	ret0, _ := ret[0].(string)
+	return ret0
+}
+
+// ProjectionName indicates an expected call of ProjectionName.
+func (mr *MockprojectionMockRecorder) ProjectionName() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ProjectionName", reflect.TypeOf((*Mockprojection)(nil).ProjectionName))
+}
+
+// Start mocks base method.
+func (m *Mockprojection) Start(ctx context.Context) {
+	m.ctrl.T.Helper()
+	m.ctrl.Call(m, "Start", ctx)
+}
+
+// Start indicates an expected call of Start.
+func (mr *MockprojectionMockRecorder) Start(ctx any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Start", reflect.TypeOf((*Mockprojection)(nil).Start), ctx)
+}
+
+// String mocks base method.
+func (m *Mockprojection) String() string {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "String")
+	ret0, _ := ret[0].(string)
+	return ret0
+}
+
+// String indicates an expected call of String.
+func (mr *MockprojectionMockRecorder) String() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "String", reflect.TypeOf((*Mockprojection)(nil).String))
+}
+
+// Trigger mocks base method.
+func (m *Mockprojection) Trigger(ctx context.Context, opts ...handler.TriggerOpt) (context.Context, error) {
+	m.ctrl.T.Helper()
+	varargs := []any{ctx}
+	for _, a := range opts {
+		varargs = append(varargs, a)
+	}
+	ret := m.ctrl.Call(m, "Trigger", varargs...)
+	ret0, _ := ret[0].(context.Context)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Trigger indicates an expected call of Trigger.
+func (mr *MockprojectionMockRecorder) Trigger(ctx any, opts ...any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	varargs := append([]any{ctx}, opts...)
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Trigger", reflect.TypeOf((*Mockprojection)(nil).Trigger), varargs...)
+}
diff --git a/internal/query/projection/projection_test.go b/internal/query/projection/projection_test.go
new file mode 100644
index 0000000000..c7b071163a
--- /dev/null
+++ b/internal/query/projection/projection_test.go
@@ -0,0 +1,69 @@
+package projection
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/brianvoe/gofakeit/v6"
+	"github.com/stretchr/testify/require"
+	gomock "go.uber.org/mock/gomock"
+)
+
+func TestStart(t *testing.T) {
+	duplicateName := gofakeit.Name()
+	tests := []struct {
+		name        string
+		projections func(t *testing.T) []projection
+		err         error
+	}{
+		{
+			name: "happy path",
+			projections: func(t *testing.T) []projection {
+				ctrl := gomock.NewController(t)
+				projections := make([]projection, 5)
+
+				for i := range 5 {
+					mock := NewMockprojection(ctrl)
+					mock.EXPECT().Start(gomock.Any())
+					mock.EXPECT().String().Return(gofakeit.Name())
+					projections[i] = mock
+				}
+
+				return projections
+			},
+		},
+		{
+			name: "same projection used twice error",
+			projections: func(t *testing.T) []projection {
+				projections := make([]projection, 5)
+
+				ctrl := gomock.NewController(t)
+				mock := NewMockprojection(ctrl)
+				mock.EXPECT().String().Return(duplicateName)
+				mock.EXPECT().Start(gomock.Any())
+				projections[0] = mock
+
+				for i := 1; i < 4; i++ {
+					mock := NewMockprojection(ctrl)
+					mock.EXPECT().String().Return(gofakeit.Name())
+					mock.EXPECT().Start(gomock.Any())
+					projections[i] = mock
+				}
+
+				mock = NewMockprojection(ctrl)
+				mock.EXPECT().String().Return(duplicateName)
+				projections[4] = mock
+
+				return projections
+			},
+			err: fmt.Errorf("projeciton for %s already added", duplicateName),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			projections = tt.projections(t)
+			err := Start(t.Context())
+			require.Equal(t, tt.err, err)
+		})
+	}
+}
diff --git a/internal/query/query.go b/internal/query/query.go
index e2e7f58ffc..7be38c6bda 100644
--- a/internal/query/query.go
+++ b/internal/query/query.go
@@ -90,7 +90,10 @@ func StartQueries(
 		return nil, err
 	}
 	if startProjections {
-		projection.Start(ctx)
+		err = projection.Start(ctx)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	repo.caches, err = startCaches(