Town maintained the unbeaten start to the season with a well earned point at Fratton Park.
Blues skipper David Norris hit the post for Blues in the closing stages, with David Nugent smacking the bar in the first-half from 15 yards for the home side in an even contest, with Town preserving the record of not losing at Portsmouth since 1966.
Connor Wickham, Damien Delaney and Mark Kennedy were all named on the bench after recovering from injury, with Town boss Roy Keane sticking with the side that beat Bristol City before the international break.
Liam Lawrence and Dave Kitson came in for their Portsmouth debuts, with Kanu and Ricardo Rocha also added to the home ranks.
Pompey started brightly and Gareth McAuley had to be alert to prevent Lawrence getting a run into the Town box. The Northern Ireland international then in the right place to head clear from Kitson's cross.
David Nugent smashed a shot against the bar just past the quarter hour after evading the Town offside trap and the home side threatened again when Nugent pulled the ball back for Hayden Mullins but he failed to take advantage.
Tamas Priskin just failed to get on the end of a Tommy Smith header from Darren O'Dea's cross, the Republic of Ireland defender included in the Blues' line-up after recovering from a knee problem.
Grant Leadbitter tested Jamie Ashdown with a curler from the edge of the box before O'Dea had to great chance to put Town ahead at the far post following a corner on the half hour, the Celtic loanee volleying over and then running into the post in the follow-up.
Norris' close range effort was hacked away after a Carlos Edwards long throw as Town began to control the game in what finished an even half after Portsmouth's strong start.
Pompey lost Aaron Mokoena inside the first few minutes of the second-half, the midfielder stretchered off with Michael Brown the replacement. Carl Dickinson then picked up the first booking of the game for a foul on Priskin.
Brown was close to making an immediate impact, forcing Marton Fulop in to a low save, the Town 'keeper then having to dive on the loose ball after Smith's clearance had rebounded off Kitson.
Fulop was in action again soon after to deal with Lawrence's 20 yarder as Pompey enjoyed a flurry of activity around the Town goal.
Jaime Peters had a cross cleared by Rocha, the Canada winger then seeing a shot blocked by the same defender as both sides searched for an opening.
Kitson hooked over from eight yards following a long throw before Portsmouth made their first change, Kanu replaced by Nadir Ciftci for the last 20 minutes.
Blues were a coat of paint away from taking the lead when Norris' 20 yard strike, after good work by Jason Scotland, rattled back off the post with Ashdown beaten before Town made two changes, Kennedy and Wickham on for O'Dea and Priskin.
Fulop produced a flying save to deny Kitson, then held firm again from Lawrence low down, while at the other end Joel Ward cleared from Leadbitter as both sides pressed for a winner.
Wickham showed a good touch to bring the ball down on the flank and carve out a corner, Luke Hyam's shot from the edge of the box blocked by Brown.
Good work down the wing by Lawrence saw the ball fall to Brown but he couldn't keep his shot down, then Norris almost forced the ball in at the other end after Wickham's shot had been beaten out by Ashdown.
John Utaka replaced Kitson in the final home change, Colin Healy on for Scotland .
Leadbitter forced Ashdown into a low save with a shot from the edge of the box, the outstanding McAuley denying Utaka with a block at the other end.
The six minutes of added on time couldn't separate the teams with Blues now looking forward to home games against the top two, QPR and Cardiff, next week.
Portsmouth: Ashdown, Ward, Sonko, Rocha, Dickinson, Lawrence, Mullins, Mokoena (Brown 50), Kitson (Utaka 86), Kanu (Ciftci 68), Nugent. Subs not used: Flahavan, Ritchie, Hughes. Booked: Dickinson.
Town: Fulop, Peters, McAuley, Smith, O'Dea (Kennedy 73), Edwards, Hyam, Leadbitter, Norris, Priskin (Wickham 73), Scotland (Healy 89). Subs not used: Murphy, Brown, Murray, Delaney.