The Icelandic international's only previous Spurs strike came in a Capital One Cup victory over Carlisle United in September.
He came off the bench to equalise for the Lillywhites at Upton Park, before Gareth Bale snatched Tottenham maximum points with an 89th-minute screamer.
Sigurdsson told the club's official website: "It's been a while. I've hit the post a few times but it's a great feeling in a London derby."
The 23-year-old turned down a move to Liverpool in favour of joining Spurs from German outfit Hoffenheim last summer.