"I have an opportunity to come back and play for the province where I grew up ... it's quite special for me," the Hastings Boys' High School product said.
"It's also an opportunity for me to be closer to my twin brothers who are 11-year-olds ... that was a big factor in my decision too."
The 2010 Super Rugby player-of-the-year Mathewson, 26, will be accompanied by his partner Cara Webber, who was one of the Bay's top swimmers and surf lifesavers during her Woodford House days, and 2-year-old son Nixon when he returns from Perth in time for the start of the ITM Cup.
A former Hurricane and Blues Super player, Mathewson, is undecided about which Hawke's Bay club he will link up with.
"I'm not sure whether the Hawke's Bay union will allocate one or if I can choose. I've got family ties with Tamatea and I also played for Havelock North and Hastings Rugby and Sports in my younger days," Matthewson recalled.
Mathewson's grandfather, the late Bill Mathewson, was a life member of the Tamatea club and his uncle, former New Zealand Colts representative Alex Mathewson, played for Tamatea.
A former New Zealand under-19 representative, Mathewson, is one of five former or current All Blacks expected to be in the Magpies squad next year. Prop Ben Franks and fullback Israel Dagg are the current ABs while Mathewson will join New Zealand Maori hooker Hika Elliot and Crusaders winger Zac Guildford as the former ABs.
In his last outing on McLean Park Mathewson scored the matchwinning try when Auckland beat the Magpies 36-29 in this season's ITM Cup opener. That was the first of the Magpies seven losses in the Cup this season.