Kal Naismith scored his first League One goal of the season to inspire Pompey to a 1-0 victory against Plymouth at Fratton Park.
The Scot poked home into an empty net midway through the first half to seal the Blues the bragging rights in the Battle of the Ports.
Brandon Haunstrup had the first real sight on goal in the 15th minute after a well-worked move, but visiting keeper Remi Matthews flicked the left-back’s effort over the bar.
Plymouth should have taken the lead in the 24th minute.
Yann Songo’o was left unmarked but headed David Fox’s free-kick high and wide.
And Pompey made the Pilgrims pay a minute later.
Matthews failed to deal with Matt Clarke’s long ball over the top and Naismith nipped in to prod the ball into an empty net.
Kenny Jackett’s troops started the second half in top gear and almost doubled their lead on 52 minutes.
Conor Chaplin intelligently picked out Gareth Evans in the box but the Blues captain had his first-time effort brilliantly saved from point-blank range by Matthews.
Naismith came agonisingly close to doubling his tally 12 minutes from time.
Chaplin stole Sonny Bradley’s back pass and thread the ball through to the former Rangers talent.
The Scot was one-on-one with oncoming Matthews, but slid his effort off the inside of the post.
Plymouth pressured for an equaliser but the Blues defending gallantly and limited the visitors to any decent chances in the closing stages.
As a result, Jackett’s men bounced back to winning ways after midweek defeat at Peterborough and moved up to seventh in League One.