The two characters were unveiled at gamescom 2011 for the forthcoming beat-'em-up, reports Comic Book Resources.
Marvel Comics' Dr Strange is the sorcerer supreme created by comics legends Stan Lee and Steve Ditko in the 1960s.
Nemesis is a monster created to hunt down the heroes of the Resident Evil games. He first appeared in Resident Evil 3: Nemesis.
They join characters including Hawkeye, Strider Hiryu, Ghost Rider and Firebrand.
Ultimate Marvel Vs Capcom 3 was announced at San Diego Comic-Con last month. The full roster was apparently leaked shortly afterwards due to an error on Capcom's media site.
Ultimate Marvel Vs Capcom 3 will be released on Xbox 360 and PlayStation 3 in November.
Watch the Ultimate Marvel Vs Capcom 3 trailer for Dr Strange below: