The historic achievement for the club, which has seen its membership figure grow by more than 20,000 since 2010, comes on the back of its successful move to the redeveloped Adelaide Oval at the end of March.
A crowd of over 50,000 spectators attended the historic first Showdown at the ground - a Power home game - where it defeated the Adelaide Crows by 54 points.
Port Adelaide now sits in the top seven of club membership figures and is rapidly gaining on its competition.
Only the Victorian powerhouses Collingwood (71,760 members), Richmond (62,826), Hawthorn (64,140), Essendon (54,537), Perth-based West Coast (53,588) and local rivals Adelaide (53,026) have higher membership tallies.
Port Adelaide's chief executive Keith Thomas hailed the achievement as significant for the club's efforts to embrace its heritage with a fully integrated 'Magpies' football program in the SANFL and aspirations to achieve sustained success in both the AFL and local league into the future.
"This is an absolute credit to our fantastic supporters who have embraced the direction the club is going in," Mr Thomas told portadelaidefc.com.au.
"To take on the big powerhouse clubs of the competition we need a large and unified membership and supporter base.
"We're working towards sustained success nationally, sustained success here in South Australia and we're doing it together as one Port Adelaide community."
While the club's successful campaign last season and promising start to 2014 has been beneficial to the club, Mr Thomas said the milestone was reached thanks to a concerted effort from the entirety of its football operations.
"Success on-field isn't enough to get this sort of figure, although it definitely helps and Ken Hinkley and Darren Burgess and our entire football department need to take the lion's share of credit for the work they've done to produce the exciting brand of footy they have since arriving at the club," Mr Thomas said.
"Our member services team has worked hard to help as many supporters become members and have been a critical piece of the puzzle.
"We need to keep this momentum going on and off the field if we want to become a standard for how AFL clubs should operate and a footy club that more people want to be part of."
Building on an internal philosophy to 'make its community proud', Port Adelaide has ticked numerous off-field boxes.
It was ranked first in the AFL for overall member satisfaction, member connection, member communication and membership arrangements in 2013, and also rated highly in media and digital growth and performance and sponsor brand recall and recognition.
Breaking the 50,000-member barrier will have significant benefit to Port Adelaide off field this year, with plenty of growth potential along its journey into the future.
The more than 20% growth on last year's total membership figure equates to an almost $2 million uplift in club revenue, while the club is also set to benefit on game days after more than doubling its number of 11-game season ticket holders since 2012.
Now focussed on the selling of three-game and general admission memberships in addition to continuing sales of other reserved seat categories with blockbuster games like this weeks' 2004 premiership commemoration against Brisbane, ANZAC Round against Geelong in Round 6 and night blockbusters against Hawthorn, Essendon, Sydney and Carlton, there is plenty of value still available for more members to join.
And with its world class stadium - labelled by some as on par with the MCG for football grounds in Australia - the club is determined to reach its next milestone quickly.
"We won't be complacent and rest on this achievement because we know there are still plenty of Port Adelaide supporters out there who haven't yet signed up," Mr Thomas said.
"What we hope is that they've seen what we did in our first game at Adelaide Oval in Round 2, because it's just the start of what we'll be doing at games this year.
"We're making going to the footy a fun family day out and the feedback we've received already has been very positive.
"I know everyone involved here - especially our players - has been really impressed with that first Showdown, so we're determined to keep bringing members on board this year and taking them on the Port Adelaide journey."
Port Adelaide memberships, including reserved seat tickets and general admission categories are available through weareportadelaide.com.au here and by calling 1300 GO PAFC.