Brendan Rodgers` side, who had lost their previous four away games, are now six points adrift of second-placed Norwich with just nine left to play for.
The Swans look now set to fight it out in the play-offs and victory at home to Ipswich on Monday, combined with results elsewhere, could clinch their top-six finish.
Pompey, who have nothing left to play for but pride, arguably shaded a very ordinary encounter, Aaron Mokoena and Hermann Hreidarsson sending what clear chances there were off target.
Only three efforts found their way on target all afternoon, although the last of which, from Swans substitute Stephen Dobbie, forced a solid parry from Jamie Ashdown deep into injury time.
Source: PA
Source: PA