The BBC One show scooped 'Best Drama Series' at the event, beating Being Human, Downton Abbey and Misfits.
Speaking to reporters after the win, Cumberbatch admitted that it was a "surprise" to hear that Sherlock had triumphed.
"It's lovely to be nominated," he said. "I know that's the patter that everyone trots out on these occasions, but it's truly the case. When you see the clips come up, you realise you are in very, very, very good company. I'm a big Misfits fan so I thought they might have [won it], but it's just terrific - it's validation for what we've been doing. To come out with an award is wonderful."
Meanwhile, Cumberbatch revealed that it's a "joy" to be back filming the new series and his co-star Martin Freeman said that they are "having a real ball".
Cumberbatch added: "The whole point of the second season is to challenge expectations. We're taking on three fantastic big stories in the Sherlock canon, so it feels comfortable but at the same time, nothing is going to be old hat. It's all going to be very big and new."
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> BAFTA TV Awards 2011: The winners in pictures
> 'TOWIE', 'EastEnders', 'Sherlock' win BAFTAs
> BAFTA TV Awards 2011: The winners in full
> BAFTA TV Awards 2011: Reaction
> BAFTA TV Awards 2011: Red carpet pictures
> Read our full coverage of the BAFTAs