Ben McKenzie and Morena Baccarin Make First Official Appearance as a Couple

Ben McKenzie and Morena Baccarin make their red carpet debut as a couple.

Ben McKenzie and Morena Baccarin are going public.

The Gotham co-stars and real-life couple attended the Sierra Club's Act in Paris, A Night of Comedy and Climate Action event at The Heath at The McKittrick Hotel in New York City, making their red carpet debut as a couple. News broke in September that the two are expecting a baby together.

Dressed in a form-fitting, high-waist number, 36-year-old Baccarin's baby bump was clearly visible. McKenzie, 37, also seemed to be comfortable around the cameras, wrapping his arm around her. Sources tell ET the two arrived hand in hand and that McKenzie was quite the gentleman, holding his girlfriend's coat while she took photos. 

Inside the event, they sat front row surrounded by Gina Gershon, Lucy Lawless, Jill Hennessy, AnnaSophia Robb, Robert De Niro, Cuba Gooding Jr, and McKenzie's Gotham co-star Erin Richards.

WATCH: Morena Baccarin Faces Her Ex in Court as Pregnancy News Surfaces

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The former Homeland actress was all smiles on Wednesday, despite a looming legal battle with her ex, Austin Chick. The father of Baccarin's 2-year-old son, Julius appears to have recently "changed his mind" about relocating to NYC where the actress films Gotham, so the two can co-parent their son together. According to new legal documents obtained by ET on Tuesday, Chick -- who was married to Baccarin for three and a half years -- decided to return to Los Angeles with his son after he learned that she "had a new boyfriend.”

Multiple sources told ET in September that Austin Chick was "shocked" and "blindsided" to find out that the pair's relationship had become more than just professional. "Totally blindsided. When Morena left him for Ben, Austin was devastated -- completely shocked," one source said.

WATCH: EXCLUSIVE -- Ben McKenzie and Morena Baccarin Plan to Marry, Her Ex 'Blindsided' By Relationship

Meanwhile, court documents released in late September revealed that Baccarin and McKenzie plan to marry.

Watch the video below for more on Baccarin and Chick's custody battle.