Dugan, 23, will now remain with the Dragons until at least the end of 2017
Sacked from his former club Canberra Raiders at the start of the 2013 season, Dugan went on to join St George, and since making his debut in round 10 he has made eight appearances, scoring four tries.
Additionally, his performances saw him selected as the New South Wales full-back for the second and third games of this year’s State of Origin Series.
Dugan said, “The club has really looked after me, made me feel very welcome and I am excited to be able to continue my football career with the Dragons.
“The Dragons have recruited strongly for next season and it was something that I really wanted to be a part of here at the club.”
Dragons head coach Steve Price was delighted the full-back has committed to the club and praised him on his transition into the team thus far.
He said, “Josh is a very talented player and I am pleased that he will continue being an important part of the team for at least the next four seasons.
“His attitude and commitment to our club since he arrived has been fantastic and his contributions to the team in games and at training has added great value to our squad.”