Pompey were forced to settle for a point as they were held to a 0-0 draw by Luton at Fratton Park.
With former Blues boss Andy Awford in charge of the visitors, Pompey had the better of the chances but were unable to find a way past an inspired Mark Tyler in the Luton goal, who made some excellent saves.
Kyle Bennett almost broke the deadlock with a fierce drive in the first half, which was beaten out by Tyler.
And after the break, Gareth Evans and Marc McNulty both had good opportunities for the home side to win the game as Pompey dominated much of the possession.
Blues goalkeeper Brian Murphy had little to do throughout the 90 minutes but Luton always carried a threat going forward on the break.
But it ended honours even as Pompey signed off 2015 with a point.