Lea helps Cory celebrate birthday
Us Weekly reported that his co-star and real-life girlfriend Lea, 26, wore a strapless grey bustier top and black pencil skirt, while Cory wore a black suit.
Lea wrote on Twitter: "A very happy birthday to the best guy I know Mr Cory Monteith. Thanks for making me feel like the luckiest girl in the world every day."
The next day Cory tweeted: "Thanks for all the birthday wishes! It was a great day. Officially old now."
The couple - who have been dating for over a year - recently returned from a relaxing holiday in Mexico, where Lea said she was planning to "rest mind, body and soul".
After Cory was released from rehab they spent some time in his home town in Canada.
Lea supported Cory throughout his treatment, saying: "I'm grateful and proud he made this decision."