Our £6m summer capture from Porto bagged his first goal just five minutes after taking the pitch as part of our second half team in the 2-0 friendly victory at Broadhall Way.
Postiga was there when it mattered to bury John Jackson's low cross in the 50th minute.
The Portugese star curled another effort just wide from 20 yards and his general play was well received by the Spurs fans in a packed crowd.
Milenko Acimovic earlier scored our first goal of the season with a cool finish from Goran Bunjevcevic's defence-splitting pass after 18 minutes.
Jamie Redknapp and Christian Ziege were the pick of the first half team as Glenn Hoddle opted to field different line-ups in each half - only goalkeeper Neil Sullivan played the full 90 minutes.
Redknapp, captain for the opening 45 minutes, was at the hub of everything from the centre of midfield and took just two minutes to hit the inside of the post after a one-two with Jamie Slabber.
Redknapp tried his luck twice more in the next 10 minutes, both gathered safely by Rob Burch, yes, that Rob Burch - guesting for the home side, in the Stevenage goal.
Slabber should have done better from close range but the opener soon arrived via Acimovic, who latched onto Bunjevcevic's slide-rule pass before finishing in style from 12 yards.
Acimovic soon flicked Ziege's wicked corner onto the top of the crossbar and the German star ended the half by bringing the best out of Burch - a full-length save to tip his curler around the post.
It was all change at half-time with the notably arrival of Helder Postiga for his first game in a Spurs shirt.
And he wasted no time in getting into the goalscoring habit, stabbing home Jackson's tempting cross from six yards just five minutes into the second half.
Gus Poyet, ever enthusiastic, fired over from 20 yards and Simon Davies will wonder how he failed to hit the target from six yards in injury time.
There were few surprises as we generally dictated play and the home side were restricted to shots from distance.
2mins: Redknapp one-two with Slabber, low shot hit inside of post and bounced to safety.
6mins: Low Redknapp shot gathered safely by Burch.
15mins: Redknapp attempted quick free-kick but Burch ready for curler.
16mins: Best chance so far, interplay between Acimovic and Ziege released Slabber who slid ball wide.
18mins: GOAL. Bunjevcevic pass split defence, Acimovic held off Laker before picking spot from 16 yards. 1-0.
25mins: Acimovic flicked Ziege corner onto the top of the crossbar.
33mins: Rare Stevenage attack ends with Holloway shooting straight at Sullivan from 20 yards.
45mins: Ziege latched onto Warner's poor backpass, shot aiming for top corner until Burch's fingertips diverted it.
Half-time: Stevenage Borough 0-1 Spurs
50mins: Jackson cross stabbed home by Postiga - just about his first touch. 2-0.
60mins: Good possession football ended with Postiga curler just wide.
71mins: Poyet fired over at the second attempt after good work from Jackson.
90mins: Davies somehow screwed wide from six yards after delightful one-two with Poyet.
Line-ups: Spurs: 1st half: Sullivan, Marney, Gardner, King, Bunjevcevic, Ziege, Anderton, Redknapp, Slabber, Acimovic, Blondel. Subs: Jalal, Hughes, Henry, Barnard, Yeates.
2nd half: Sullivan, Ricketts, Taricco, Toda, Kelly, Perry, Davies, Postiga, Poyet, Jackson, Etherington. Subs: Jalal, Hughes, Henry, Barnard, Yeates.
Stevenage Borough: 1st half: Burch, Warner, Flynn, Goodliffe, Laker, Wormull, Battersby, Cook, Carroll, Holloway, Elding.
2nd half: Burch, Travis, Gould, Langston, Costello, Watson, Richards, Forinton, Baptiste, Laker, Flynn.
Helder Postiga made an immediate impact on his Spurs debut at Stevenage Borough on Monday night.