Although he had only been in town a couple of days, he said the town had a "nice climate" and people were "pretty friendly".
His wife, Rose, and their four children who range from ages one to eight will stay in Wellington until the end of the school term.
Mr Gallagher was born and bred in the Wairarapa and has worked in every police station in the region.
After four years in Masterton and five in Eketahuna, it was back to Masterton and now to Carterton.
Mr Simpson has spent most of his policing career in the Bay of Plenty, but has moved to Carterton from Wellington.
He said the lifestyle attracted him as well as the "all-in-one challenge" of policing a small town.
"You do a bit of everything, really, but in the big city you tend to specialise a bit more."
His partner will join him at the end of the school term.
Wairarapa police senior sergeant Carolyn Watson said the changes were due to other staff leaving.
"It's exciting to have new staff in Carterton who bring with them experience from other areas.
"All are experienced in community policing and they're looking forward to the challenging environment of policing here."
Sergeant Kevin Basher and Constable Hayden Robinson also work from the Carterton station.