Danielle Rowe’s first league goal for Pompey Women was not enough to prevent a 2-1 defeat at Cardiff.
Nia Rees and Jasmine Simpson struck either side of the interval to give the hosts a commanding advantage.
Rowe’s close-range finish gave the Blues hope of a comeback in the Welsh capital, but they were unable to find a leveller.
Jay Sadler handed a debut to new signing Alex Collighan for the National League encounter, following a 14-0 rout over Eastleigh in the Hampshire Cup the previous week.
The two sides sat closely together in the table and the visitors knew victory would have seen them leapfrog their opponents.
Both sides took a while to find their feet in an even start to the contest, but Pompey had the first decent chance when Daisy McLachlan controlled Eilidh Currie’s pass and fired over.
Debutant Collighan almost had an opportunity to open the scoring, with Currie’s cross just evading the onrushing winger.
The Blues backline was looking resilient and it took a 25-yard strike from Rees to break the deadlock on 32 minutes.
They were still enjoying a large amount of possession as the interval loomed, but were unable to find a response.
Half Time: Cardiff 1 Pompey 0
Sadler made a double change at the start of the second half, with Hannah Geer and Sarah Eadon replacing EJ May and Carla Perkins.
And Pompey emerged quickly from the blocks, as Jade Bradley saw her drive from the edge of the box held by Laura O’Sullivan.
Despite that positive opening, it was Cardiff who were next to score – albeit against the run of play – on 55 minutes.
Simpson received the ball just outside the area and curled a shot right into the top corner of Robyn Levett’s net.
Eadon was keen to make an impact following her brace against Eastleigh and soon saw an effort deflected narrowly past the post.
But the Blues did find a route back into the game when pressure from ROWE paid off, as she stole the ball from a defender and tapped home.
Cardiff stayed strong at the back, however, and despite coming under late pressure, they held on to claim all three points.
Pompey: Levett; Currie, Younger (James 82), Southgate (c), Tonks; Rowe, Perkins (Geer 46); May (Eadon 46), Bradley, Collighan; McLachlan
Subs not used: Kirby, Anu
Next up for Pompey Women is a trip to Carshalton’s War Memorial Sports Ground, where they face AFC Wimbledon in the second round of the FA Cup.
It is a repeat of last season’s fixture at the same stage of the competition, with the Blues battling from behind to win 2-1 on that occasion.