After Norwich's 2-1 win against Nottingham Forest on Friday night, the Bluebirds went into the encounter knowing they needed three points to lift themselves back into an automatic promotion spot.
And they secured just that thanks, in the main, to a fluent attacking display full of endeavour.
That intent was epitomised by Craig Bellamy, who began a scintillating performance by setting up Seyi Olofinjana's opener.
Pompey's cause was then hampered when Ricardo Rocha received an 18th-minute red card.
The Bluebirds capitalised on their one-man advantage with goals from Jay Bothroyd and Peter Whittingham capping an excellent effort.
Despite the importance of the clash, the Bluebirds started in confident fashion with Bellamy and Bothroyd looking particularly menacing.
And they took the lead in the eighth minute through Olofinjana.
Bellamy was the orchestrator, capitalising on a clever ball from Bothroyd to jink down the right wing before sending in a delicious centre which Olofinjana gleefully headed home.
Portsmouth tried to get back into the game but their chances were hampered considerably midway through the opening period when Rocha was dismissed for appearing to headbutt Bothroyd.
That sparked unsavoury scenes, with the centre-half having to be restrained as he left the field.
Pompey's problems were almost compounded from the resulting free-kick as Whittingham hit just over the crossbar.
Dave Jones' side continued to dominate and could have grabbed a second, but, after being found by Bellamy's excellent cross, Bothroyd headed just wide.
Any hopes the visitors had of getting back into the game all but evaporated on the stroke of half-time as Bothroyd got the goal his industry deserved.
Whittingham's corner caused chaos in the Portsmouth box and, after several ricochets, the ball fell to the former Blackburn striker, who was left with the simplest of finishes.
Picking up where they left off, Cardiff assumed control of proceedings once again after the interval although Portsmouth were threatening with a counter-attacking approach.
The match entered a lull in the second period, with the hosts seemingly content to retain possession.
Chances still came fleetingly, though, with Bothroyd almost netting his second when he saw his goal-bound effort blocked by Aaron Mokoena.
The Bluebirds did get a third in the 73rd minute when Bellamy showed great vision to find Whittingham, who slotted home his 10th goal of the season to wrap up the points.