diff --git a/pkg/training/error.go b/pkg/training/error.go
index a9bdc11..aedd058 100644
--- a/pkg/training/error.go
+++ b/pkg/training/error.go
@@ -3,6 +3,7 @@ package training
 import "errors"
 
 var (
-	ErrTrainingNotFound     = errors.New("training not found")
-	ErrTrainingDateNotFound = errors.New("training date not found")
+	ErrTrainingNotFound             = errors.New("training not found")
+	ErrTrainingDateNotFound         = errors.New("training date not found")
+	ErrTrainingDateAttendeeNotFound = errors.New("training date attendee not found")
 )
diff --git a/pkg/training/repository.go b/pkg/training/repository.go
index 8a1edc9..81fa595 100644
--- a/pkg/training/repository.go
+++ b/pkg/training/repository.go
@@ -193,3 +193,105 @@ func (r *InMemoryTrainingDateRepository) Delete(id TrainingDateID) error {
 
 	return nil
 }
+
+type TrainingDateAttendeeRepository interface {
+	Create(trainingDateID TrainingDateID, attendee *TrainingDateAttendee) error
+	FindByID(id TrainingDateAttendeeID) (*TrainingDateAttendee, error)
+	FindAll() ([]TrainingDateAttendee, error)
+	FindAllByTrainingDateID(trainingDateID TrainingDateID) ([]TrainingDateAttendee, error)
+	Update(attendee *TrainingDateAttendee) error
+	Delete(id TrainingDateAttendeeID) error
+}
+
+type InMemoryTrainingDateAttendeeRepository struct {
+	attendees       map[TrainingDateAttendeeID]TrainingDateAttendee
+	dateToAttendees map[TrainingDateID][]TrainingDateAttendeeID
+
+	lock sync.RWMutex
+}
+
+func NewInMemoryTrainingDateAttendeeRepository() *InMemoryTrainingDateAttendeeRepository {
+	return &InMemoryTrainingDateAttendeeRepository{
+		attendees:       make(map[TrainingDateAttendeeID]TrainingDateAttendee),
+		dateToAttendees: make(map[TrainingDateID][]TrainingDateAttendeeID),
+	}
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) Create(trainingDateID TrainingDateID, attendee *TrainingDateAttendee) error {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	attendee.ID = NewTrainingDateAttendeeID()
+	attendee.trainingDateID = trainingDateID
+
+	r.attendees[attendee.ID] = *attendee
+	r.dateToAttendees[trainingDateID] = append(r.dateToAttendees[trainingDateID], attendee.ID)
+
+	return nil
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) FindByID(id TrainingDateAttendeeID) (*TrainingDateAttendee, error) {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	attendee, ok := r.attendees[id]
+	if !ok {
+		return nil, ErrTrainingDateAttendeeNotFound
+	}
+	return &attendee, nil
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) FindAll() ([]TrainingDateAttendee, error) {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	attendees := make([]TrainingDateAttendee, len(r.attendees))
+	for _, attendee := range r.attendees {
+		attendees = append(attendees, attendee)
+	}
+
+	return attendees, nil
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) FindAllByTrainingDateID(trainingDateID TrainingDateID) ([]TrainingDateAttendee, error) {
+	r.lock.RLock()
+	defer r.lock.RUnlock()
+
+	attendees := make([]TrainingDateAttendee, 0)
+	for _, id := range r.dateToAttendees[trainingDateID] {
+		attendees = append(attendees, r.attendees[id])
+	}
+
+	return attendees, nil
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) Update(attendee *TrainingDateAttendee) error {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	oldAttendee := r.attendees[attendee.ID]
+	attendee.trainingDateID = oldAttendee.trainingDateID
+	r.attendees[attendee.ID] = *attendee
+	return nil
+}
+
+func (r *InMemoryTrainingDateAttendeeRepository) Delete(id TrainingDateAttendeeID) error {
+	r.lock.Lock()
+	defer r.lock.Unlock()
+
+	attendee, ok := r.attendees[id]
+	if !ok {
+		return ErrTrainingDateAttendeeNotFound
+	}
+
+	delete(r.attendees, id)
+	attendees := r.dateToAttendees[attendee.trainingDateID]
+	for idx, a := range attendees {
+		if a == id {
+			r.dateToAttendees[attendee.trainingDateID] = append(attendees[:idx], attendees[idx+1:]...)
+			break
+		}
+	}
+
+	return nil
+}