Bangor-born Broadhead was in the final year of his contract with Ipswich, where he scored 23 goals in 83 appearances.
Last season Broadhead, who started his professional career at Everton, scored two goals in 18 Premier League games for Kieran McKenna’s side.
“He’s just got that Championship pedigree, the ability to create something in tight situations, you need players to unlock the door and create key moments in games and Nathan’s got that,” Parkinson added.
“He’s shown it at Ipswich at levels over the past few seasons and obviously the story of him coming home is a great one as well.
“He was really keen to come here and I’m really looking forward to working with him.”
