Hermann Hreidarsson (65) fired Pompey ahead, thanks to a fine ball from substitute Kanu.
Dindane wasted a spot-kick – after a dubious penalty awarded to Hreidarsson – and a presentable rebound chance after half an hour, but made no mistake when he sealed Pompey’s third win of the season from Jamie O’Hara’s cross.
Steven Fletcher passed up a trio of chances and Kevin McDonald saw his effort saved by Asmir Begovic before Pompey took the lead.
Hreidarsson found himself in the left side of the penalty area and collected a smart flick from Kanu before firing left-footed into the far corner.
And Dindane (84) then headed home the second at the far post after O’Hara’s deep cross to lift Pompey off the bottom of the table.