The 36-year-old actress appeared to confirm her relationship with Fischer in the post from Ellen DeGeneres' 60th birthday party, which took place Saturday in Los Angeles.
The black and white picture shows Schumer embracing Fischer as they share a kiss at the photo booth.
"Happy Birthday @theellenshow thank you for having us!" Schumer captioned the photo.
Schumer and Fischer, a chef, were first linked in November after being spotted at dinner in New York, according to Us Weekly. The actress split from Ben Hanisch in May after more than a year of dating.
"Amy and Ben have ended their relationship after thoughtful consideration and remain friends," her rep told People at the time.
Schumer will next star in the movie I Feel Pretty, which opens June 29. She discussed the film with DeGeneres on Thursday's episode of The Ellen DeGeneres Show, describing it as a "funny and sweet" movie.
"It's about my character, Renee," the actress said. "She kind of has low self-esteem. She really wants to be pretty and wants to feel all the parts of life that open up to you when you're just like, gorgeous."
"I fall off my bike in SoulCycle and I start seeing myself as a supermodel," she added. "I look exactly the same, but in my mind, I'm Gisele [Bundchen]."