Portsmouth striker Yakubu scored his fifth goal of the season and his second in as many matches to condemn Tottenham to only their second defeat of the season.
Yakubu headed a deserved Portsmouth winner midway through the second half as Tottenham conceded for the only the fourth time since their French coach Jacques Santini took charge in the summer.
Portsmouth made by far the brighter start with Lomana Tresor LuaLua racing past Spurs defender Noe Pamarot, himself a former Fratton Park loanee, three times in the opening four minutes.
LuaLua should have done better when, after outpacing the hapless Pamarot, he screwed a right-foot shot wide from the edge of the area.
England centre-back Ledley King was presented with Tottenham's first chance of the game when he outjumped a static Pompey defence before heading narrowly over from Timothee Atouba's fourth minute corner.
Pompey's response to that scare was impressive with Yakubu and Eyal Berkovic both going close from the same move.
Patrik Berger lobbed the ball through to Yakubu with a typical extravagant pass and the Nigerian saw his first-time shot beaten away by Paul Robinson.
Berkovic should have finished the job when Robinson's punch landed straight into his path but the Israeli midfielder suffered a rush of the blood to the head and blazed over.
Yakubu came close again in the 20th minute after being put through by LuaLua but Pompey's top scorer miscontrolled the ball with the goal gaping.
Robinson pulled off another fine save to turn over Berger's close-range shot in the 24th minute.
The fit again Serbian defender Dejan Stefanovic then saw a header saved by Robinson from Berkovic's free-kick.
And Stefanovic was on hand to help deny Jermain Defoe the opening goal a minute from half time.
Defoe found himself bearing down on Shaka Hislop after a neat one-two with Robbie Keane but the pint-sized striker fluffed his kick under pressure from the alert Stefanovic.
Berkovic completed his brace of misses four minutes into the second half.
Man-of-the-match LuaLua broke free on the left touchline before pulling the ball back for Berkovic who scuffed a poor shot wide from 18 yards.
Hislop then pulled off a superb tip-over to keep out Defoe's 18-yard piledriver.
But the Trinidadian could only watch as defender Anthony Gardner smashed a header against a post from Michael Brown's free-kick seconds later.
Defoe went close again with a shot on the turn from Keane's cross in the 54th minute which sailed just over.
But Yakubu got the goal the home side deserved nine minutes later, heading home from four yards out from LuaLua's right-wing cross.
Even the arrival of midfielder Michael Carrick for his Tottenham debut could not lift Santini's side.
The Portsmouth fans, still bitter from Carrick's summer snub, booed the former West Ham player's every touch.
And Pompey could have added a second goal when their own sub Diomansy Kamara volleyed wide from midway inside the penalty area eight minutes from time.