Mathewson, 33, joined the club on a four-month contract in August last year as cover when Conor Murray was ruled out of action due to a neck injury.
However, he ended up staying with the club for 15 months and making a big impression on the Munster faithful.
Mathewson had earlier started his link with Munster when making his All Blacks debut in the memorable 18-16 win in Limerick in 2008. It took a late try before the All Blacks managed to avoid what would have been their second loss to the Irish side.
Once joining the side as a playing member, after a 19-game stint with Toulon in France, he played 28 times and scored six tries. He marked his debut for the side by contributing to a record win over Ulster.
His last game at the weekend was the 21–21 draw with Racing 92 at Thomond Park secured with a late conversion.
Mathewson told Munster fans in an Instagram post: "Thank you Munster Rugby and all the supporters for the last 15 months. I've had an unbelievable time and feel honoured to have been able to wear the Munster jersey.
"I'm lucky to have experienced European rugby at Thomond Park and see why it is one of the best atmospheres in the world to play in front of and how much this team means to the community and its supporters."
He added he would miss his team mates and the craic and banter of their locker room before training.
"It's been 15 months but it feels like it's flown by. I've had no family over here but the boys here are my family and the support from them and the supporters is just overwhelming," he told Munsterrugby.ie.
Mathewson said it was often the case that short-term players didn't make an effort to adapt to the side but his attitude was to come in, do his best and earn the respect of team mates and fans and to 'truly buy-in to what it means to be a Munster man'.
"Being here for 15 months I've learnt what that's all about. I'm just glad I was part of that and I've made memories that I'll never forget from here," he said.