"I Can't Tell You Why" is a song by the American rock band Eagles, which appeared on their 1979 album The Long Run. It was written by band members Timothy B. Schmit, Glenn Frey, and Don Henley. Recorded in March 1978, it was the first song finished for the album and the first Eagles song to feature Schmit on lead vocals. Released as a single in February 1980, it became a Billboard top 10 hit in April of that year, reaching number eight on the Billboard Hot 100 and number three on the Adult Contemporary chart. It was the group's last top ten hit on the Billboard Hot 100.