Pethrus Gärdborn began to play the flute at the age of nine as a student of Jan Bengtson, Associate Principal flute with the Royal Stockholm Philharmonic, and Stig Bengtson, Principal Flute Emeritus with the Royal Opera Orchestra of Stockholm. At the age of eleven, he performed the Vivaldi Piccolo Concerto in C Major at The Royal Chapel in Stockholm under the baton of Mats Liljefors. He continued to be engaged as a soloist, chamber musician and orchestral musician in Sweden as well as internationally, gathering substantial experience already as a young player. In 2005, Gärdborn was awarded first prize in The Scandinavian Championship for Wind Instruments in Oslo. Further studies under Dr. Bradley Garner at the College-Conservatory of Music in Cincinnati, USA, brought about more first prizes in flute competitions such as: The National Flute Association Piccolo Artist Competition in 2006 Pittsburgh, The Frank Bowen Young Artist Competition in 2008 Albuquerque, New Mexico, and The Myrna Brown Young Artist Competition in 2008 Denton, Texas.
Composer Kyle Werner has dedicated his Concerto for Flute and Strings to Pethrus who performed the World Premiere in Cincinnati in 2008. Pethrus has also collaborated with Kyle Werner in his other ensemble and orchestral compositions and worked together with other contemporary composers in the MusicX Festival for Contemporary Music in Blonay, Switzerland.
As an orchestral musician, Pethrus Gärdborn has worked in the major orchestras in Sweden, such as The Royal Opera Orchestra, The Royal Stockholm Philharmonic, The Swedish Radio Symphony, The Malmö Symphony Orchestra, The Norrköping Symphony Orchestra and The Helsingborg Symphony Orchestra.