"I got the call from (Mariners coach Graham Arnold) Arnie pretty late on in the piece and it's all been a bit of a rush, but I'm looking forward to catching up with a lot of familiar faces at the Mariners," said Henderson.
"Commuting to Newcastle has been tough but heading to Gosford is only half the trip, so I'm looking forward to cutting down on my travel time!"
The 34-year-old Sydneysider made his NSW Premier League debut for Sutherland Sharks back in 1996 before becoming the inaugural goalkeeper at Northern Spirit in the National Soccer League in 1998.
After five seasons and more than 100 appearances in the UK, Henderson returned to Australia to join North Queensland Fury last Hyundai A-League season, and most recently, has been on injury replacement secondment at the Newcastle Jets.
Henderson will wear squad number 30 during his six-week short-term injury replacement deal, and will be available to come into the squad for tomorrow's clash against Sydney FC at the Sydney Football Stadium.