It was only in the second half that Arsenal's fluid passing game began to get going and even when it was up and running the visitors proved unable to consistently test James.
That had much to do with a superb display from Sol Campbell in the Portsmouth defence as Pompey became the first side to stop Arsenal scoring this season in the league.
Arsenal began and finished the first half at a brisk pace, but in between Portsmouth dominated proceedings.
Emmanuel Eboue showcased his marauding ability on the right of midfield in those early stages, while as the first half drew to a close, James was twice called into action.
James's save from Rosicky's shot demonstrated the Portsmouth goalkeeper's superb athleticism.
The trajectory of Rosicky's shot looked to have beaten James, but he somehow managed to elongate his dive that little bit extra to clutch hold of the ball.
James showed he was equally adept at reading the game as he rushed out of the box to get the ball ahead of Emmanuel Adebayor.
With just Kanu in attack, Harry Redknapp's side lacked the necessary numbers to regularly test the Arsenal defence.
Almunia only had two moments of real concern in those frenetic opening 45 minutes.
Benjani put in a dangerous cross early on, while Kranjcar went close with a shot from just outside the box.
Benjani had the clearest opening of the match when his intelligent run was picked out by Kanu.
The former Auxerre star managed to go past Almunia but his touch took him too wide and Arsenal cleared the danger.
In the closing minutes Gallas shot over from close range, while Rosicky went agonisingly close with a low fizzing shot.
Pompey boss Harry Redknapp:
"We aren't defensive but it's difficult when you haven't got the ball and there is no team harder to get the ball off in England than Arsenal.
"You have to be disciplined or you will get ripped to pieces. To keep a clean sheet against Arsenal is fantastic.
"We worked our socks off and this is a great point for us, well deserved."
Arsenal manager Arsene Wenger:
"I was surprised they defended so much, even their midfield was focused solely on defending.
"In the second half Pompey did not come out of their half - offensively they did not play too well, but they just had Kanu playing up front on his own.
"I guess they got the maximum they could from this type of game. They made it very, very difficult for us."
Portsmouth:
James, Lauren, Campbell, Distin, Hreidarsson, Mwaruwari (Utaka 81), Diop, Hughes, Muntari, Kranjcar (Taylor 76), Kanu.
Subs Not Used: Begovic, Traore, Nugent.
Booked:
Lauren, Diop.
Arsenal:
Almunia, Sagna, Toure, Gallas, Clichy, Eboue (Diaby 65), Flamini, Fabregas, Hleb (Bendtner 82), Rosicky, Adebayor.
Subs Not Used: Lehmann, Diarra, Song Billong.
Booked:
Eboue.
Att:
20,556
Ref:
Steve Bennett (Kent).
BBC Sport Player Rater man of the match:
Cesc Fabregas 7.45 (on 90 minutes).
Please note that you can still give the players marks out of 10 on BBC Sport's Player Rater after the match has finished.
