diff --git a/api/handler.go b/api/handler.go
index 95c6260..eb7e213 100644
--- a/api/handler.go
+++ b/api/handler.go
@@ -44,6 +44,7 @@ func Handler() *mux.Router {
 	m.Get(router.ObservationType).Handler(handler(serveObservationType))
 	m.Get(router.CreateObservationType).Handler(handler(serveCreateObservationType))
 	m.Get(router.ObservationTypes).Handler(handler(serveObservationTypeList))
+	m.Get(router.UpdateObservationType).Handler(handler(serveUpdateObservationType))
 
 	return m
 }
diff --git a/api/observation_types.go b/api/observation_types.go
index 3242cb3..cbf28c9 100644
--- a/api/observation_types.go
+++ b/api/observation_types.go
@@ -57,3 +57,22 @@ func serveObservationTypeList(w http.ResponseWriter, r *http.Request) error {
 
 	return writeJSON(w, observation_types)
 }
+
+func serveUpdateObservationType(w http.ResponseWriter, r *http.Request) error {
+	id, _ := strconv.ParseInt(mux.Vars(r)["Id"], 10, 0)
+	var observation_type models.ObservationType
+	err := json.NewDecoder(r.Body).Decode(&observation_type)
+	if err != nil {
+		return err
+	}
+
+	updated, err := store.ObservationTypes.Update(id, &observation_type)
+	if err != nil {
+		return err
+	}
+	if updated {
+		w.WriteHeader(http.StatusOK)
+	}
+
+	return writeJSON(w, observation_type)
+}
diff --git a/api/observation_types_test.go b/api/observation_types_test.go
index ee00d7f..4469695 100644
--- a/api/observation_types_test.go
+++ b/api/observation_types_test.go
@@ -94,3 +94,33 @@ func TestObservationType_List(t *testing.T) {
 		t.Errorf("got observation_types %+v but wanted observation_types %+v", observation_types, want)
 	}
 }
+
+func TestObservationType_Update(t *testing.T) {
+	setup()
+
+	want := newObservationType()
+
+	calledPut := false
+	store.ObservationTypes.(*models.MockObservationTypesService).Update_ = func(id int64, observation_type *models.ObservationType) (bool, error) {
+		if id != want.Id {
+			t.Errorf("wanted request for observation_type %d but got %d", want.Id, id)
+		}
+		if !normalizeDeepEqual(want, observation_type) {
+			t.Errorf("wanted request for observation_type %d but got %d", want, observation_type)
+		}
+		calledPut = true
+		return true, nil
+	}
+
+	success, err := apiClient.ObservationTypes.Update(want.Id, want)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !calledPut {
+		t.Error("!calledPut")
+	}
+	if !success {
+		t.Error("!success")
+	}
+}
diff --git a/datastore/observation_types.go b/datastore/observation_types.go
index bff1da8..1bebeec 100644
--- a/datastore/observation_types.go
+++ b/datastore/observation_types.go
@@ -46,3 +46,26 @@ func (s *observationTypesStore) List(opt *models.ObservationTypeListOptions) ([]
 	}
 	return observation_types, nil
 }
+
+func (s *observationTypesStore) Update(id int64, observation_type *models.ObservationType) (bool, error) {
+	_, err := s.Get(id)
+	if err != nil {
+		return false, err
+	}
+
+	if id != observation_type.Id {
+		return false, models.ErrObservationTypeNotFound
+	}
+
+	observation_type.UpdatedAt = time.Now()
+	changed, err := s.dbh.Update(observation_type)
+	if err != nil {
+		return false, err
+	}
+
+	if changed == 0 {
+		return false, ErrNoRowsUpdated
+	}
+
+	return true, nil
+}
diff --git a/datastore/observation_types_test.go b/datastore/observation_types_test.go
index addd956..86b66c0 100644
--- a/datastore/observation_types_test.go
+++ b/datastore/observation_types_test.go
@@ -85,3 +85,23 @@ func TestObservationTypesStore_List_db(t *testing.T) {
 		t.Errorf("got observation_types %+v, want %+v", observation_types, want)
 	}
 }
+
+func TestObservationTypesStore_Update_db(t *testing.T) {
+	tx, _ := DB.Begin()
+	defer tx.Rollback()
+
+	observation_type := insertObservationType(t, tx)
+
+	d := NewDatastore(tx)
+
+	// Tweak it
+	observation_type.ObservationTypeName = "Updated Obs Type"
+	updated, err := d.ObservationTypes.Update(observation_type.Id, observation_type)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if !updated {
+		t.Error("!updated")
+	}
+}
diff --git a/models/observation_types.go b/models/observation_types.go
index 7ae69ab..a785a3a 100644
--- a/models/observation_types.go
+++ b/models/observation_types.go
@@ -34,6 +34,9 @@ type ObservationTypesService interface {
 
 	// Create an observation type record
 	Create(observation_type *ObservationType) (bool, error)
+
+	// Update an existing observation type
+	Update(id int64, observation_type *ObservationType) (updated bool, err error)
 }
 
 var (
@@ -109,10 +112,32 @@ func (s *observationTypesService) List(opt *ObservationTypeListOptions) ([]*Obse
 	return observation_types, nil
 }
 
+func (s *observationTypesService) Update(id int64, observation_type *ObservationType) (bool, error) {
+	strId := strconv.FormatInt(id, 10)
+
+	url, err := s.client.url(router.UpdateObservationType, map[string]string{"Id": strId}, nil)
+	if err != nil {
+		return false, err
+	}
+
+	req, err := s.client.NewRequest("PUT", url.String(), observation_type)
+	if err != nil {
+		return false, err
+	}
+
+	resp, err := s.client.Do(req, &observation_type)
+	if err != nil {
+		return false, err
+	}
+
+	return resp.StatusCode == http.StatusOK, nil
+}
+
 type MockObservationTypesService struct {
 	Get_    func(id int64) (*ObservationType, error)
 	List_   func(opt *ObservationTypeListOptions) ([]*ObservationType, error)
 	Create_ func(observation_type *ObservationType) (bool, error)
+	Update_ func(id int64, observation_type *ObservationType) (bool, error)
 }
 
 var _ ObservationTypesService = &MockObservationTypesService{}
@@ -137,3 +162,10 @@ func (s *MockObservationTypesService) List(opt *ObservationTypeListOptions) ([]*
 	}
 	return s.List_(opt)
 }
+
+func (s *MockObservationTypesService) Update(id int64, observation_type *ObservationType) (bool, error) {
+	if s.Update_ == nil {
+		return false, nil
+	}
+	return s.Update_(id, observation_type)
+}
diff --git a/models/observation_types_test.go b/models/observation_types_test.go
index 81ffb48..cf53cfb 100644
--- a/models/observation_types_test.go
+++ b/models/observation_types_test.go
@@ -112,3 +112,34 @@ func TestObservationTypeService_List(t *testing.T) {
 		t.Errorf("ObservationTypes.List return %+v, want %+v", observation_types, want)
 	}
 }
+
+func TestObservationTypeService_Update(t *testing.T) {
+	setup()
+	defer teardown()
+
+	want := newObservationType()
+
+	var called bool
+	mux.HandleFunc(urlPath(t, router.UpdateObservationType, map[string]string{"Id": "1"}), func(w http.ResponseWriter, r *http.Request) {
+		called = true
+		testMethod(t, r, "PUT")
+		testBody(t, r, `{"id":1,"observation_type_name":"Test Obs Type Updated","created_at":"0001-01-01T00:00:00Z","updated_at":"0001-01-01T00:00:00Z","deleted_at":{"Time":"0001-01-01T00:00:00Z","Valid":false}}`+"\n")
+		w.WriteHeader(http.StatusOK)
+		writeJSON(w, want)
+	})
+
+	observation_type := newObservationType()
+	observation_type.ObservationTypeName = "Test Obs Type Updated"
+	updated, err := client.ObservationTypes.Update(observation_type.Id, observation_type)
+	if err != nil {
+		t.Errorf("ObservationTypes.Update returned error: %v", err)
+	}
+
+	if !updated {
+		t.Error("!updated")
+	}
+
+	if !called {
+		t.Fatal("!called")
+	}
+}
diff --git a/router/api.go b/router/api.go
index bf0cabd..a1bbf34 100644
--- a/router/api.go
+++ b/router/api.go
@@ -35,6 +35,7 @@ func API() *mux.Router {
 	m.Path("/observation_types").Methods("GET").Name(ObservationTypes)
 	m.Path("/observation_types").Methods("POST").Name(CreateObservationType)
 	m.Path("/observation_types/{Id:.+}").Methods("GET").Name(ObservationType)
+	m.Path("/observation_types/{Id:.+}").Methods("PUT").Name(UpdateObservationType)
 
 	return m
 }
diff --git a/router/routes.go b/router/routes.go
index 332f374..ca63317 100644
--- a/router/routes.go
+++ b/router/routes.go
@@ -26,4 +26,5 @@ const (
 	ObservationType       = "observation_type:get"
 	CreateObservationType = "observation_type:create"
 	ObservationTypes      = "observation_type:list"
+	UpdateObservationType = "observation_type:update"
 )