Irishman McGeady joins the Black Cats at the second time of asking
McGeady, who spent last season on loan with Simon Grayson's then Preston side, signs a three-year contract while former Everton man Vaughan has put pen to paper on a two-year deal.
Speaking to the club's official website following the announcement of the pair, Grayson described McGeady as an "exceptional player" whose career "speaks volumes".
The 31-year-old was named the Lilywhites' Player of the Year after scoring eight league goals and grabbing as many assists last season. Grayson praised him as an "outstanding performer at Preston" and promised that he is a player who will "excite the supporters" with pace and trickery.
Interestingly, McGeady was the subject of a €9m bid from current Republic of Ireland boss Martin O'Neill's Sunderland whilst a Spartak Moscow player in 2012 but a move never materialised.
The trickster's career has seen him play for Celtic, Spartak Moscow, Everton, Sheffield Wednesday and most recently Preston with the 31-year-old also making 90 appearances for the Republic of Ireland since 2004.
Vaughan ready for another crack at the Championship
Vaughan is the more expensive of the two new signings with his fee reportedly around the £500,000 mark. He arrives with a pedigree to his name after becoming the Premier League's youngest ever goalscorer with Everton aged just 16 in April 2005.
Grayson told the club's official website that his side "were missing a striker with a physical presence" prior to the signing of Vaughan, adding that the former Everton man "certainly brings that attribute."
The Black Cats boss added that "he fits in with the ethos that we’re trying to bring to Sunderland", which is something that he made a point of prioritising upon arriving in the North-East.
The 28-year-old finished last season as League One's second top scorer for 19th placed Bury with 24 league goals to his name, representing the most successful season of his career so far.
The striker has become a bit of a journeyman since a promising start to his career, with his list of clubs including Derby County, Leicester City, Crystal Palace, Norwich City, Huddersfield Town, Birmingham City and most recently Bury before his Wearside move.
The pair add to a number of former Everton players currently in the Sunderland squad, with summer signings Tyias Browning and Brendan Galloway the most recent arrivals while Jack Rodwell, Bryan Oviedo and Darron Gibson have also turned out for the Toffees in previous years.