Betty White is mourning the loss of a friend.

The 95-year-old actress took to Twitter on Thursday to pay tribute to Mary Tyler Moore, sharing a sweet throwback photo of "some of the best times" of their lives.

FLASHBACK: Inside the 'Mary Tyler Moore Show' 2002 Reunion With Betty White and Valerie Harper

"Mary Tyler Moore, Grant Tinker, Allen Ludden and I had some of the best times of my life together," she wrote alongside the throwback pic. "She was special."

EXCLUSIVE: Carl Reiner Reveals His Last Words to Mary Tyler Moore, Says Her Final Days Were in Hospice Care

Moore died on Wednesday in Greenwich, Connecticut, of cardiopulmonary arrest after contracting pneumonia, the actress' rep confirmed to ET. She was 80. 

White and Moore starred together on The Mary Tyler Moore Show in the 1970s, and Moore spent her last television appearance guest-starring on White's TV Land Sitcom, Hot in Cleveland.

"It's wonderful, but it makes me sad too. It makes me feel, well, why don't I have this in my current life?" Moore told ET of the reunion, which also featured Valerie Harper, Cloris Leachman, and Georgia Engel, at a press conference for the special episode.

"Where are all these friends, buddies, and co-workers, and people who loved each other? Why can't they be around?" she continued. "Or maybe they can."

EXCLUSIVE: Ed Asner Remembers His Friend Mary Tyler Moore: 'Whenever She Needed Me, I Was Ready to Serve'

See more in the video below.