Maddock said that he is returning to New Zealand with his family and was keen to thank the coaching staff for helping him during his time at Saracens.
"I'm heading back to New Zealand," he told the club's official website. "Work wise I'm still on the hunt for when I return, but as a family we decided that the time was right for us to go back.
"Saracens as a club is an awesome place to be. The club is full of great people; people who work extremely hard for each other and for the organisation as a whole.
"From my point of view the coaching staff have been brilliant with me, the backroom staff have done their bit to help me look after my body and the players who I train with every week and I get to play with occasionally are just good blokes."
Maddock joined Saracens in 2010.