diff --git a/src/github.com/matrix-org/dendrite/federationapi/routing/join.go b/src/github.com/matrix-org/dendrite/federationapi/routing/join.go
index d06b243b9..99e8d82de 100644
--- a/src/github.com/matrix-org/dendrite/federationapi/routing/join.go
+++ b/src/github.com/matrix-org/dendrite/federationapi/routing/join.go
@@ -16,6 +16,7 @@ package routing
 
 import (
 	"context"
+	"encoding/json"
 	"net/http"
 	"time"
 
@@ -89,5 +90,62 @@ func SendJoin(
 	keys gomatrixserverlib.KeyRing,
 	roomID, eventID string,
 ) util.JSONResponse {
+	var event gomatrixserverlib.Event
+	if err := json.Unmarshal(request.Content(), &event); err != nil {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.NotJSON("The request body could not be decoded into valid JSON. " + err.Error()),
+		}
+	}
 
+	// Check that the room ID is correct.
+	if event.RoomID() != roomID {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.BadJSON("The room ID in the request path must match the room ID in the join event JSON"),
+		}
+	}
+
+	// Check that the event ID is correct.
+	if event.EventID() != eventID {
+		return util.JSONResponse{
+			Code: 400,
+			JSON: jsonerror.BadJSON("The event ID in the request path must match the event ID in the join event JSON"),
+		}
+	}
+
+	// Check that the event is from the server sending the request.
+	if event.Origin() != request.Origin() {
+		return util.JSONResponse{
+			Code: 403,
+			JSON: jsonerror.Forbidden("The join must be sent by the server it originated on"),
+		}
+	}
+
+	// Check that the event is signed by the server sending the request.
+	verifyRequests := []gomatrixserverlib.VerifyJSONRequest{{
+		ServerName: event.Origin(),
+		Message:    event.Redact().JSON(),
+		AtTS:       event.OriginServerTS(),
+	}}
+	verifyResults, err := keys.VerifyJSONs(httpReq.Context(), verifyRequests)
+	if err != nil {
+		return httputil.LogThenError(httpReq, err)
+	}
+	if verifyResults[0].Error != nil {
+		return util.JSONResponse{
+			Code: 403,
+			JSON: jsonerror.Forbidden("The join must be signed by the server it originated on"),
+		}
+	}
+
+	// TODO: Fetch state and auth events
+
+	return util.JSONResponse{
+		Code: 200,
+		JSON: map[string]interface{}{
+			"state":      []gomatrixserverlib.Event{},
+			"auth_chain": []gomatrixserverlib.Event{},
+		},
+	}
 }
diff --git a/src/github.com/matrix-org/dendrite/federationapi/routing/routing.go b/src/github.com/matrix-org/dendrite/federationapi/routing/routing.go
index 5d921b3c5..4f2ff4e52 100644
--- a/src/github.com/matrix-org/dendrite/federationapi/routing/routing.go
+++ b/src/github.com/matrix-org/dendrite/federationapi/routing/routing.go
@@ -136,6 +136,18 @@ func Setup(
 		},
 	)).Methods("GET")
 
+	v1fedmux.Handle("/send_join/{roomID}/{userID}", common.MakeFedAPI(
+		"federation_send_join", cfg.Matrix.ServerName, keys,
+		func(httpReq *http.Request, request *gomatrixserverlib.FederationRequest) util.JSONResponse {
+			vars := mux.Vars(httpReq)
+			roomID := vars["roomID"]
+			userID := vars["userID"]
+			return MakeJoin(
+				httpReq.Context(), httpReq, request, cfg, query, time.Now(), keys, roomID, userID,
+			)
+		},
+	)).Methods("PUT")
+
 	v1fedmux.Handle("/version", common.MakeExternalAPI(
 		"federation_version",
 		func(httpReq *http.Request) util.JSONResponse {