The 25-year-old has spent the last three seasons with Sheffield’s British Basketball League (BBL) rivals and previously played for the Grevenbroich Elephants in Germany.
Originally from Wilmington, Delaware he appeared in 86 matches for the Bristol Flyers with a career average of 9.1 points and 5.0 rebounds per game.
“I’m excited to be part of a historically successful organisation that is always in the playoff hunt,” said Delpeche, a graduate of Bates College in Maine who stands at 6ft 7ins.
“I really enjoyed my time in Bristol but I’m ready for this next step and looking forward to seeing what Sheffield has to offer.
"I actually have family from the area so it will be great to connect with and have them at the home games.”
Fans will be allowed to return to Ponds Forge to watch the Sharks in action this season after they were locked out last term because of coronavirus restrictions.
British passport holder Delpeche joins long-serving captain Mike Tuck and Jordan Ratinho as the first players to sign up for the 2021/22 season with Sheffield.
“Marcus has certainly made an impact on us over the years, said head coach Atiba Lyons.
"His size and athleticism are things that always jump out at you immediately, but he is also committed, consistent, and is one of those players that just puts their heads down and works.
"I’m really looking forward to maximising his abilities here in Sheffield.”
Sheffield Sharks finished fifth in the regular season last time out.