"She's so much more of a woman and powerful, courageous, fearless and all those adjectives. And I look at her with awe," he said in an interview with Meredith Vieira for NBC's "Today."
Vieira also talked to Fawcett's friend, Alana Stewart, for reports airing on the "Today" show Wednesday and Thursday.
O'Neal and Stewart participated in the documentary titled "Farrah's Story," a video diary of the actress' fight against anal cancer that has spread to her liver. The film airs Friday on NBC.
O'Neal and the "Charlie's Angels" star had a long romantic relationship that ended in the late 1990s and are parents of a son, Redmond O'Neal.
Ryan O'Neal said Fawcett has managed to joke about her illness and his own battle against chronic myelogenous leukemia, which was diagnosed in 2001.
"She asked me once, 'Am I gonna make it?' She asked me that a couple of weeks ago," O'Neal recounted. "I said, 'Yeah, sure, you'll make it. And if you don't, I'll go with you.'
Fawcett then joked that he should stop taking Gleevec, the medicine O'Neal uses to treat leukemia, he said.
"She's the rock. She taught us all how to cope," O'Neal said. "She's extraordinary. I don't know what I'll do without her, to tell you the truth."
Copyright 2009 The Associated Press.