Listen to Mammas, Don't Let Your Babies Grow Up to Be Cowboys online. Mammas, Don't Let Your Babies Grow Up to Be Cowboys is an English language song and is sung by Waylon Jennings and Willie Nelson. Mammas, Don't Let Your Babies Grow Up to Be Cowboys, from the album The Essential Willie Nelson, was released in the year 2015. The duration of the song is 2:31. Download English songs online from JioSaavn.