Dubnyk began his professional career in 2006 with the Stockton Thunder of the ECHL where he compiled a strong 24–11–7 record. His 24 wins, 2.56 GAA and .921 save percentage set club records and he was selected to be an ECHL All-Star for the 2006–07 season. In 2007–08, he began to play full-time for what was then Edmonton's American Hockey League (AHL) affiliate, the Springfield Falcons. In three seasons with the Falcons, Dubnyk played 128 games, compiling a 40–75–4 record. In 2008–09, Dubnyk set a club record for most appearances by a goaltender with 62.