It looked like being a familiar tale for the Blues when Caolan Lavery fired them ahead midway through the first half.
But the Magpies soon levelled through Graham Burke’s fine strike and a second half Alan Sheehan free-kick somehow found its way into the net.
The visitors could feel somewhat hard done by, however, as they contributed plenty to a chance-filled contest.
Paul Cook made two changes from the side that drew with Mansfield at Fratton Park the previous week.
Gareth Evans returned from suspension to take his place wide on the right, while there was also a start for the fully-fit Adam McGurk, with Kal Naismith and Rommy Boco the men to make way.
Before kick-off there was a minute’s silence in memory of all those who have lost their lives in conflict.
When the game got underway it quickly turned into an open affair, with both sides contributing to an entertaining affair.
Pompey came close to breaking the deadlock on seven minutes, but Adam Webster could not quite divert Ben Davies’ corner on target.
The home support were then cheering when former Blues striker Izale McLeod had the ball in the net moments later, although referee Andy Haines had long since blown his whistle for offside.
And the action soon switched back down to the other end of the pitch, where Sheehan was on hand to hack clear after Roy Carroll had slowed down Evans’ drive.
County then enjoyed a spell of possession in Pompey’s half and Brian Murphy denied McLeod before beating away a curling effort from Burke.
But it was the Blues who broke the deadlock on 20 minutes, as LAVERY opened his account for the club.
Kyle Bennett and Enda Stevens combined well down the left and the latter delivered a low cross that Lavery deftly turned into the bottom corner.
They were only ahead for a matter of minutes, however, as a free-kick was cleared as far as Burke, who struck a fine volley into the net from the edge of the box.
Lavery tried to restore the visitors’ advantage on 30 minutes, only to see his low angled drive kept out by Carroll, while Evans was then millimetres away from connecting with Bennett’s dangerous cross.
But it was Webster who went closest to scoring again before the break, surging forward from the halfway line before firing a shot against the inside of the post.
There were half-chances for both sides as the seconds ticked down, with Liam Noble and McGurk both unable to find the target from long-range.
But it took fine headed clearance from Mike Edwards to prevent Lavery from converting Davies’ cross in stoppage-time.
Notts County 1
The second half started in the same way that the first had finished – with both sides keen to get forward.
And the hosts survived when Bennett’s effort cannoned off a defender and was just about kept in play by Carroll.
Then, at the other end, McLeod opted to lay the ball off for Burke rather than shoot, with Danny Hollands gratefully nipping in to intercept.
McGurk was next to go close on 57 minutes, only to see his effort inadvertently blocked by Evans at close range.
Lavery then collected Bennett’s sweeping pass and curled in a shot that Sheehan did well to get in the way of.
Bennett had penalty appeals turned down just past the hour mark after the winger felt he had been tripped in the area, while Evans’ follow-up was deflected into the side netting.
Cook made his first change on 67 minutes, with the tiring McGurk making way for Conor Chaplin.
But the hosts then enjoyed a spell of sustained pressure and won a couple of corners before Murphy had to come charging from his box to clear the danger.
Pompey responded with a second substitution on 76 minutes, as Ben Tollitt made his first league appearance in place of Bennett.
But the hosts were ahead within seconds, with Sheehan’s long-range free-kick – won for a foul on McLeod – evading everyone on its way into the net.
Matt Tubbs was immediately brought on as the shell-shocked Blues went in search of a late leveller.
Notts County held firm at the back for the final few minutes, however, as Pompey were finally vanquished on the road.
Notts County (4-1-4-1): Carroll (c); Hewitt, Edwards, Sheehan, Barmby; Aborah; Stead, Noble (Thompson 86), Smith (De Silva 72), Burke (Campbell 60); McLeod
Goals: Burke 23, Sheehan 77
Subs not used: Loach, Amevor, Jenner, Spencer
Pompey (4-2-3-1): Murphy; Davies, Burgess, Webster, Stevens; Hollands, Doyle (c); Evans, McGurk (Chaplin 67), Bennett (Tollitt 76); Lavery (Tubbs 80)
Goals: Lavery 20
Subs not used: Bass, Clarke, Atangana, Naismith
Referee: Andy Haines
Attendance: 6,917 (2,162 Pompey fans)