The All-Australian midfielder has been the focus of a concerted poaching effort from Geelong to lure the Victorian home but has opted to re-commit to the Power.
Boak attributes Port's improved 2013 form as a key reason for re-signing to the end of the 2018 season.
"The club's come a long way in the last 12 months or so with the additions of Ken (Hinkley) and (chairman David) Kochie and with the new players coming in, it's even more exciting!" he said.
Port coach Ken Hinkley said Boak was central to his young club.
"The people who play with him fall in behind him. Like a typical captain he gets them all going," he said.
After growing up in the Victorian coastal town Torquay, where his family still lives, and playing for Geelong Falcons as a teenager, Boak was once considered likely to eventually find his way to the Cats.
In 2012, Geelong's courting of Boak extended to coach Chris Scott and senior players Joel Selwood and Jimmy Bartel travelling to Adelaide to pitch directly to Boak.
After months of speculation, Boak signed to the end of the 2014 season and was rewarded with the Port captaincy this year.
His sparkling form helped Port finish well above expectations in sixth and earned Boak his first All-Australian nod.
Boak was drafted with Port Adelaide's first selection in the 2006 draft from the Geelong Falcons, and will be 30-years-old when his new contract expires.
Port have announced the re-signing of four other key players during the week, leading goalkicker Jay Schulz (to the end of 2015), vice captain Brad Ebert (2017), and midfielders Hamish Hartlett and Jake Neade (2016).