Despite not registering a win since the opening day of the season, Yeovil Town threatened to leave Suffolk with a shock victory after Joel Grant's stunning strike just before half-time.
But second half goals from Daryl Murphy and Aaron Cresswell saw Mick McCarthy's men grind out a hard-fought victory.
Fresh from their 3-1 home win at Middlesbrough on Saturday, Ipswich set about their visitors right from the first whistle.
The returning Murphy, twice, and Ryan Tunnicliffe both tested Wayne Hennessey's goal with varying degrees of accuracy in the opening minutes.
It set the tone for much of the half, one that threatened to spark into life without ever really doing so.
Ipswich created the better openings without truly testing the Wolves loanee keeper.
The dangerous David McGoldrick went closest, Hennessey having to save a low 20-yarder at the second attempt, while Yeovil could only enjoy possession rather than opportunities.
In-form McGoldrick was getting closer, again drifting past the flat-footed Seaborne, but missing the far corner by inches, before Yeovil took a shock lead three minutes before the interval.
Williams left three home defenders trailing as he ran left to right, before Grant - a target for Town in the summer - picked up the ball and unleashed an unstoppable left-foot drive into the top corner.
Yeovil began the second half brighter but Williams could only find the side-netting when through on goal. He was made to pay seven minutes after the restart.
A patient build-up from Ipswich ended with Cole Skuse heading back across goal and Murphy scoring at the second attempt, off his knee after initially hitting the underside of the crossbar.
Town's tails were up and McGoldrick almost added a second just minutes later but fired high with the unmarked Tunnicliffe waiting for the pass.
But they did not have to wait long to grab the lead through an unlikely source on the hour-mark.
Shaping to shoot, McGoldrick teed up the onrushing Cresswell. The left-back's initial low cross was blocked by Liam Fontaine but Cresswell had time to confidently slide the rebound high into the far corner.
As the game entered the final 10 minutes, Ipswich cranked up the pressure.
Murphy was denied a second when his close-range header was blocked by Kieffer Moore before headers from Luke Hyam and Tommy Smith teed up Christophe Berra but Hennessey denied him, diving low to his left for the best save of the night.
Yeovil almost snatched an injury-time equaliser when Joe Ralls had time in the area but his low shot was pushed away by Dean Gerken.