Centre-back Daniel Ballard has joined the club from Arsenal and will be hoping to make an immediate impact after impressing while on loan at Millwall last season.
The Black Cats have also been able to agree new deals with Bailey Wright, Patrick Roberts and Lynden Gooch, after their previous contracts expired.
So what's Alex Neil's strongest side as it stands?
1. GK: Anthony Patterson
After an impressive end to the 2021/22 season, the 22-year-old academy graduate will hope to start the new campaign as Sunderland's No 1. The Black Cats will need to bring in someone to challenge Patterson, though. Preferably it'll be someone with Championship experience. Photo: JPI Media
2. RB: Carl Winchester
Neil has said he sees the Northern Irishman as a right-sided defender, while Winchester, 29, was one of the club's most consistent performers during the 2021/22 season. Still, the Black Cats will be looking to strengthen in the full-back areas. Photo: JPI Media
3. CB: Daniel Ballard
Sunderland's new signing isn't guaranteed a starting place (after Bailey Wright and Danny Batth formed a robust partnership at the end of last season), yet he arrives on Wearside with Championship experience and lots of potential to improve. The 22-year-old impressed during a loan spell at Millwall during the last campaign, when he made 31 second-tier appearances. Photo: Jacques Feeney
4. CB: Bailey Wright
The Australian centre-back, 29, started every game following Neil's arrival in February and was a key player under the Scot. Wright's performances earned him a new two-year deal on Wearside, after he helped Australia qualify for this year's World Cup. Photo: Frank Reid