The Raiders, who are one of four teams to have earned promotion to the Championship for next season, take on Doncaster at the Halliwell Jones Stadium on Sunday.
Dawson, 23, has made 22 appearances in his first year with the club, while Scotland international Nixon is close to breaking in to the club’s top 10 all-time try scorers list.
Raiders Director of Rugby Andy Gaffney said: “We are well aware that we will need a very strong pack of forwards if we are to survive in the Championship and there is no more promising prop forward than Andy. He is going to get better and better with each season and I am really pleased that he is going to continue in a Raiders’ shirt for the next twelve months.
“(I’m) delighted James has agreed to extend his time at the club. He is one of only a handful of players ever to have scored 100 tries for Barrow and without doubt he is one of quickest wingers in the sport.