Marek Saganowski reignited Saints' promotion push as Southampton moved back into the play-off places. Gareth Bale set up the Polish striker's first-minute goal, swinging in a free-kick that Saganowski nodded in.
Ten minutes into the second half Kenwyne Jones turned inside the area and hit a shot that struck the post.
Alex Bruce headed narrowly over the bar in the first half for Ipswich, while substitute Jonathan Walters' header forced Kelvin Davis into a smart save.
Saints manager George Burley:
"It was an vital win. There are a lot of clubs vying for the play-offs. "Lots of teams are dropping points and Sunderland are on a good run, so we really needed the three points.
"It keeps us in the top six, which is where we want to be."
Ipswich boss Jim Magilton:
"On a run like we're on, you will find yourself in the relegation battle. "What we've got to do is take away that fear factor and get the players believing they can win a game.
"We had a shocking start in the game and it is another game we have lost by the odd goal."
Southampton: Davis, Makin, Baird, Lundekvam, Bale, Belmadi (Pele 76), Wright, Viafara, Surman, Jones, Saganowski (Wright-Phillips 83).
Subs Not Used: Bialkowski, Rasiak, Dyer.
Booked: Belmadi.
Goals: Saganowski 1.
Ipswich: Price, Wright, De Vos, Bruce, Harding, Garvan, Richards (Peters 68), Legwinski, Roberts, Lee (Haynes 82), O'Callaghan (Walters 69).
Subs Not Used: Supple, Casement.
Booked: Roberts.
Att: 27,974.
Ref: R Olivier (W Midlands).