The Egyptian star announced his arrival with a two-goal show, dragging us back from an undeserved 1-0 deficit and pushing us on our way to a deserved win.
He was in electric form in his 62-minute stint, lashing over as early as the fourth minute all the way through to his final, most decisive touch - sliding home Jermain Defoe's cross to give us the lead after 56 minutes.
Mido was replaced by Robbie Keane and Keano made the game safe with a typical, improvised goal, lobbing home Andy Reid's pass with the outside of his right foot with eight minutes left.
That pass from Reid capped his afternoon's work down the left flank after he'd earlier struck the woodwork.
So both new arrivals Mido and Reid made their debuts, Mido replacing suspended Fredi Kanoute. Noureddine Naybet returned for Anthony Gardner while Thimothee Atouba started at left-back for Erik Edman, who joined Keane on the bench.
Mido made an immediate impression in the first half. He was involved straight away, lashing over after three minutes and then crossing for Stephen Kelly to head straight at Chalkias.
Ledley King had a half-chance when he could only guide Andy Reid's corner, Mido's near-post cross was deflected into the side-netting by Stefanovic and it looked like a goal was on it's way.
It was - but at the other end. Pompey only had Berger's wild lash into Paxton Road to show for the first 28 minutes but went ahead with their first effort on target, Kamara getting the flick from Berger's inswinging corner.
Thankfully, it didn't take us long to reply. Defoe had appeals for a penalty waved away when Mido struck, powering home his header from Davies' cross after 33 minutes.
Portsmouth did have the ball in the net again but Kamara was correctly penalised for handling the ball around the advancing Robinson and it stayed 1-1 at the break.
We were soon back on the front foot in the second half with Mido taking a whack as he headed Defoe's cross over.
Mido then headed Reid's corner wide, made a superb dummy run to allow Defoe an effort at goal and curled as shot from 20 yards that Chalkias held low to his right.
We were getting up a head of steam now and it was no surprise when Mido put us 2-1 up. Pompey made a hash of a clearance, Defoe latched onto the loose ball, beat Taylor and drilled in a cross from the byline to leave Mido with the easiest of tasks.
Mido was soon on his way to a standing ovation and there was a lull in the goalmouth action after that as we controlled possession.
Despite a couple of substitutions, Portsmouth simply couldn't get a foothold in the game and Robinson only had one save to make from Yakubu's volley into the ground.
Defoe had the next chance, an attempted dink read by Chalkias and the striker then linked up with Reid, whose shot beat Chalkias but came back off the left upright.
A third goal was always on the cards and followed seconds after, this time Reid floating the perfect pass into Keane who expertly lobbed Chalkias with the outside of his right foot to secure the points.
GUIDE TO THE ACTION
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3mins: Mido's first notable action in a Spurs shirt, on the end of decent move as Atouba played in Davies, he laid the ball back and Mido lashed over from 20 yards.
6mins: Great work from Atouba to get onto Reid's pass down left touchline, dug superb cross out that Chalkias just managed to flick away from Mido. Mido picked up loose ball on right, measured cross to Kelly who looped header at Chalkias. Started well.
7mins: CHANCE. Reid's corner landed at feet of King who could only guide it wide from eight yards.
10mins: Davies attempted tricky volley from edge of area, sailed wide.
14mins: Good feet from Mido wide left, whipped in cross to near post that Stefanovic deflected into side-netting.
26mins: Berger blazed well wide from 30 yards.
28mins: GOAL. Berger's inswinging corner flicked home at near post by Kamara. Pompey's first effort on target.
Spurs 0, Portsmouth 1
32mins: PENALTY? Lovely flick from Mido into Defoe, got in front of de Zeeuw and went down, looked like Stefanovic had a grab.
33mins: GOAL. Move started by King, Defoe played wide to Davies, pinpoint cross found Mido who powered home header from 10 yards.
Spurs 1, Portsmouth 1
42mins: DISALLOWED: Ball over the top released Kamara who handled it around Robinson and slotted home. Referee on spot for the handball.
Half-time: Spurs 1,Portsmouth 1
46mins: Clash of heads as Mido went in for Defoe's cross with Primus, both players okay to continue.
49mins: Mido up to meet Reid's corner but couldn't keep header on target.
50mins: Defoe used Mido's run to create a yard on edge of box, drilled a left-foot shot that led to painful block by Stefanovic.
55mins: Mido curler from 20 yards taken comfortably to his right by Chalkias.
56mins: GOAL. Defoe latched onto loose ball in box, beat Taylor, drilled in low cross from byline tapped in by Mido.
Spurs 2, Portsmouth 1
57mins: Brown went charging in to meet Carrick's corner, won it, ball just over.
59mins: Defoe found a yard of space at far post from Reid's corner, control and hit shot that was on its way until Taylor blocked.
60mins: Cisse curled just over from 25 yards.
62mins: SUBS. Keane for Mido; Fuller and Mezague for Berger and O'Neill.
67mins: Yakubu spun on bouncing ball from free-kick, Robinson alert and made save look easy.
81mins: CHANCE. Clever pass from Davies into Defoe as Pompey looked for offside, Defoe controlled but attempted dink over Chalkias saved.
82mins: WOODWORK. Lovely little pass around the corner from Defoe to Reid, took shot early, cannoned back off foot of left post.
82mins: GOAL. Reid pass over the top to Keane who lifted bouncing ball over stranded Chalkias and into far corner.
Spurs 3, Portsmouth 1
83mins: SUB. Bunjevcevic for Naybet.
88mins: SUB. Skopelitis for Primus.
Injury time: Defoe shot blocked, Carrick onto rebound and shot just wide from 22 yards.
Spurs: Robinson, Kelly, Atouba, King, Naybet (Bunjevcevic, 83); Davies, Brown, Carrick, Reid; Mido (Keane, 62), Defoe. Subs: Cerny, Edman, Marney.
Portsmouth: Chalkias, Primus (Skopelitis, 88), Stefanovic, de Zeeuw, Taylor, Cisse, Yakubu, Kamara, Hughes, Berger (Fuller, 60), O'Neill (Mezague, 60). Subs: Ashdown, Rodic.
Mido made a stunning debut as we got back to winning ways in the Barclays Premiership against Portsmouth at the Lane on Saturday.