Goals from Thierry Henry and Alex Hleb either side of the break secured maximum points, but a more emphatic margin of victory would have been achieved had the Gunners' finishing matched their approach play.
Arsene Wenger opted to make two changes to the team which defeated Sheffield United 3-0 at the weekend. Emmanuel Adebayor and Freddie Ljungberg dropped to the bench, with Hleb and Robin van Persie replacing them.
The Gunners boss was also forced to make a late switch when Johan Djourou picked up an injury during the warm-up. Justin Hoyte stepped up from the bench.
The hosts started well and thought they had taken the lead after just four minutes when Kolo Toure bundled the ball home from a corner. However, the linesman ruled the ball had gone out of play before reaching the Ivorian.
It looked only a matter of time until Arsenal actually opened the scoring, as Hleb, Tomas Rosicky and van Persie knocked the ball about nonchalantly in midfield while the visiting defenders chased shadows.
However, for a ten-minute period in the middle of the first half Porto dominated, with Ricardo Quaresma threatening to rip the home defence apart.
It proved to be only a brief spell of dominance for the visitors and Arsenal, with van Persie at the centre of everything they did, soon regained the initiative.
The Dutchman squandered a good chance by firing over after being played in by Henry, before seeing Porto goalkeeper Helton make good low save to deny him.
It was no surprise when the goal eventually arrived in the 38th minute, but it was a shock that van Persie was not involved.
For once Arsenal swapped their intricate passing game for a direct approach and it paid dividends. Emmanuel Eboue surged down the right and sent over a perfect out-swinging cross for Henry to head home at the far post.
A looping van Persie header almost doubled the hosts' advantage just before the break, but they had to wait for less than three minutes after the restart for a second goal.
William Gallas made a purposeful run through midfield before squaring the ball to Henry on the edge of the penalty area. The Frenchman stretched to square it to the on-rushing Hleb, who despatched a low shot beyond Helton.
It was game over as soon as Hleb's shot nestled in the back of the net.
Porto had few ideas going forward and Lehmann had only two saves to make -comfortable takes from substitute Raul Meireles and Quaresma.
Arsenal were happy to show off rather than test the Porto goalkeeper and while Henry's silky skills entertained the crowd, the hosts rarely looked like adding a third.
That will have been of little concern to Wenger, as his side already have one foot in the draw for the first knockout round.