The Snatch director told USA Today that although he is normally against making sequels, he "couldn't help" joining forces with Robert Downey Jr (Holmes) and Jude Law (John Watson) again.
"I can't help myself. They wanted this to be a franchise, which, in my mind, needs at least two movies," he joked. "But I really liked working with the team on the first movie, so this was an easy choice."
Sherlock Holmes: A Game of Shadows will see the famous detective pitted against his nemesis James Moriarty, played by Jared Harris.
Ritchie praised Harris's take on the villain, saying: "Moriarty is one of the most famous villains of all time. But we didn't want to make him a conventional character. The challenge was to still make him modern, believable.
"Jared brings a depth, a realism, that everyone was really excited about. He's very relatable."
Sherlock Holmes: A Game of Shadows will be released in cinemas on December 16.
> Sherlock Holmes 2 character posters released
Watch Robert Downey Jr and Jude Law on the set of Sherlock Holmes: A Game of Shadows below: