The 28-year-old Auckland-born front rower joined the Sea Eagles back in 2018 and has since played 53 games in Manly stripes.
Manly CEO, Tony Mestrov commented on Sipley's re-signing in a club release stating, "Toff (Sipley) is a hard-working prop who just constantly strives to get better each and every day.
"I know how proud everyone was for Toff when he played his 50th game for the Sea Eagles last season. It was a real testament to his work ethic and professionalism as he has had to overcome some tough knee injuries in recent years.
"You can see at training every day just how much positivity and energy he brings. Toff is always smiling and encouraging people at the club, be it teammates or staff.
"We know Toff's game will only getter better and he will again be a key man in our strong forward pack."
Sipley will partner Manly recruit, Ben Condon in the front row on Friday night when he captains the Sea Eagles in their pre-season challenge match against South Sydney in Gosford.