"What a Fool Believes" is a song written by Michael McDonald and Kenny Loggins. The best known version was recorded by The Doobie Brothers for their 1978 album Minute by Minute (with McDonald singing lead vocals and Michael Jackson backing voice). The single reached number one on the Billboard Hot 100 on April 14, 1979, remaining in that position for one week. The song received Grammy Awards in 1980 for both Song of the Year and Record of the Year.
"What a Fool Believes" was one of the few non-disco No. 1 hits on the Billboard Hot 100 during 1979.
Michael Jackson claimed to have contributed at least one backing track to the original Doobie Brothers recording, but was not credited for having done so.