"I Can't Tell You Why" is a song by the American rock band Eagles, which appeared on their 1979 album The Long Run. The song 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.
Schmit describes the song as "loosely based on my own experiences". Schmit said: "I had some writing sessions with Don and Glenn and I threw out a bunch of my ideas and that one [for "I Can't Tell You Why"] stuck. I had [composed] a pretty good part of it, not a huge part but enough for them to think 'That could be good' and go with it. So Don, Glenn and I finished it over a few all night sessions."
Schmit said: "When it was being developed in the studio...I knew it was a great song. I [thought] 'Yes! This is an amazing debut for me.' When we finally mixed it, we had a little listening party at the studio. As people were hearing it, Don turned to me and said, 'There's your first hit.'"