"It would have been nice, especially considering the impact she had on the awards season, but Cooper and I have been overwhelmed with support and love over my mom's passing and we choose to focus on that," Rivers said in a statement posted on Facebook.
The Academy issued its own statement earlier Monday.
"Joan Rivers is among the many worthy artists and filmmakers we were unfortunately unable to feature in the In Memoriam segment of this year's Oscar show. She is, however, included in our In Memoriam gallery on Oscar.com," the statement said.
Fans on social media complained about Rivers' absence from the tribute. Elaine Stritch was also a notable omission from the entertainment world, though her career was built on stage, not on screen.
Rivers was also not well-known for her film work, though she made a regular sideline out of her snarky critiques of red-carpet fashion.