The couple has never officially confirmed their relationship, but moved in together last fall and were frequently spotted together. While promoting their film, "Case 39," Cooper gushed over his female co-star.
"I can't say enough about her," Cooper said in September. "I just love her. I [loved] coming to work. I love acting with her. I can learn so much from her."
In January, Zellweger missed the Golden Globe awards after a fire broke out at Cooper's mother's Philadelphia-area home while the two celebrities were with the family. The couple were visiting Philadelphia after Cooper's father died on January 15.
By February, there was speculation that the couple was not doing well when they attended a pre-Oscar party but did not spend time together.
Cooper is currently promoting his psychological thriller, "Limitless" which hit theaters on Friday, the actor appeared on "Inside the Actors Studio" on Monday where host James Lipton brought the actor to tears. Zellweger was in the audience for the actor's appearance.
The actor's reps have no comment on the reports.