The 31-year-old forward and former club captain formally announced his decision this afternoon at a press conference at the club's Mt Smart headquarters.
Mannering will make his 294th club appearance in Sunday's home game against Melbourne and is on track to play his 300th game in the Warriors' final-round clash against Canberra on August 31. He will go beyond the triple-century if the side maintains its course to make their first finals appearance since 2011.
Mannering's pending retirement comes after he struggled to make a decision throughout the first half of the year as he weighed up whether to continue playing into a 15th season in 2019.
"It has taken a while to reach this point but I'm now comfortable with the decision I've finally made," Mannering said.
"It hasn't been easy that's for sure. There has been a lot to think about. I've really enjoyed this season and that was one of the factors that was playing on my mind.
"I'm really grateful to the Vodafone Warriors for giving me the time I needed. It's a big call when you consider retirement, even more so having played my whole career for this great club.
"It's not over yet, though. There are still a lot of games to be played and I want to do all I can to help the team and the coaching staff in our bid to finish this season as well as we possibly can."
The former Kiwis skipper's recent retirement from international football prior to the Denver test, after playing 45 tests and in three World Cups, was a pointer that he might be looking for a new career path.
Mannering's decision also comes after he produced his best performance of the season in Sunday's emphatic 26-6 victory over Brisbane at Suncorp Stadium that saw him wind back the clock with a titanic display in both attack and defence.
That effort renewed hope that he might feel energized enough to continue playing but he will now look to channel all his energy into one last tilt at the club's elusive first premiership title win.
The Napier-born product is understood to be considering taking up a job either as a quantity surveyor or in carpentry as he looks towards life beyond football.
