Listen to Mammas Don't Let Your Babies Grow up to Be Cowboys (feat. Willie Nelson) online. Mammas Don't Let Your Babies Grow up to Be Cowboys (feat. Willie Nelson) is an English language song and is sung by Waylon Jennings. Mammas Don't Let Your Babies Grow up to Be Cowboys (feat. Willie Nelson), from the album This Is Outlaw Country, was released in the year 1998. The duration of the song is 2:33. Download English songs online from JioSaavn.