The King of Pop died at age 51 from a lethal dose of the anesthetic propofol in 2009.
Houston told Winfrey that his passing was "devastating".
With her voice shaking, the troubled songstress added, "I thought, 'This can't be true. This can't be true.' I knew he was on painkillers at one time. I didn't know how far and how deep it was."
Houston recalled taping Michael Jackson's 30th Anniversary Celebration with the King of Pop in 2001. Both stars appeared extremely frail at the event.
The singer remembered looking at Jackson and then looking at herself. "I was getting scared," she admitted. "I was looking at myself going, 'No, I don't want this to be like this. This can't happen. Not both of us.'"
Houston —- whose own substance abuse issues have long been documented -— revealed to Winfrey that she had been doing drugs at the time of the Jackson taping.
She said she "was worried" for him -- and for herself. "Mike and I were very close," Houston said. "No one have I ever met [was] quite like that young man," she later added. "And to have it in like that saddens me."
"Was he a mirror for you," Winfrey asked Houston.
"In some ways, yes," the diva replied. "I didn't want to go down that road."
Like Jackson, Houston was on the verge of a career comeback before her Feb. 11 passing.
A coroner's official says Houston's body was discovered underwater in a hotel bathtub (some prescription drugs were in her room).
It will take weeks to determine precisely how the megastar died.
A private funeral is set for Saturday in the New Jersey church where Houston first showed off her singing talents as a child.
- Michael Jackson