Pétur Grétarsson studied percussion at Reykjavík College of Music and later jazz, percussion and composition at Berklee College of Music in Boston.
He has been active on the Icelandic music scene for 25 years. Pétur Grétarsson has performed regularly with Iceland Symphony Orchestra. He has given solo recitals and has appeared with miscellaneous ensembles performing his own and other composers' music.
Many of his creations are related to theatres and he has composed film music as well.
Furthermore he has been a productive programmer for radio.
Pétur Grétarsson is the artistic director of Reykjavík Jazz Festival.