The character, made popular in "The Lord of the Rings" trilogy, changed Serkis' career. He would later do motion capture work in "King Kong" and in "Rise of the Planet of the Apes."
He said playing Gollum has a special place in his heart.
"Not only was it the first character for me that sort of pushed along the performance capture technology, that was the role that really enabled me to play all the others," he said.
Now Serkis has a totally different new role.
"The Hobbit" director, Peter Jackson, asked him to direct the trilogy's second unit.
The three films were shot back-to-back-to-back.
"I literally, from going out for two weeks to reprise the role of Gollum, I was suddenly faced with a year and half shooting for 200 days, massive crew, big sets, shooting battle sequences and aerial shots and working with a great cast and learning from one of the greatest filmmakers on Earth," Serkis said.
In some theatres, "The Hobbit" will be shown in 3-D at 48 film frames per second. That's double what you've been watching on screen for the past 90 years.
It's a brand new big screen experience.
"It's the most unbelievably immersive, engaging, thrilling - you feel like you're inside the movie," he said. "It's like an enormous feast that you can really dig into and enjoy this journey with these incredibly varied and lovable and crazy characters."
The film is in theaters now. It's rated PG-13.