Martyn Waghorn gave Ipswich the lead against the run of play when he swept the ball past keeper Daniel Bentley.
Bartosz Bialkowski made two good saves before Nico Yennaris hit the bar and Florian Jozefzoon missed a free header as Brentford went close to equalising.
But Joe Garner doubled Town's lead with a powerful header from a corner to help Mick McCarthy's side clinch the win.
Ipswich had failed to win any of their past five Championship matches against Brentford, but goals from summer signings Waghorn and Garner saw them extend their 100% start to the season.
Waghorn has hit the ground running since joining from Rangers earlier this month and scored his fourth goal of the campaign, following good work from David McGoldrick.
Brentford had their chances, with Kamohelo Mokotjo and Ollie Watkins going close, but Garner's header, which was confirmed by goalline technology, ensured Ipswich kept pace with Cardiff City at the top of the Championship.
Former Rangers strike duo Waghorn and Garner have now scored a combined seven goals in just seven Championship appearances between them.
Ipswich manager Mick McCarthy:
"It was a thoroughly professional performance against a very good side. Everyone put in a shift and I could praise everybody for their performance.
"Bart (Bialkowski) made the saves when needed and it was just a whole team performance.
"Last season we didn't look like scoring at all and we do this year. It's lovely for the lads, for me and the supporters to see goals go in. They are a threat and it's great to see."
Brentford boss Dean Smith:
"That's certainly the word I'd use at the moment, frustration. We made one mistake in the first half and they score. We should have been out of sight in the first half, we were excellent.
"We created a number of chances and didn't take them. I believe if we score when we're on top then we win the game comfortably.
"We have to keep believing in what we're doing. I'm optimistic, but I'm cautious that we're losing games which we shouldn't lose."
Match ends, Ipswich Town 2, Brentford 0.
Second Half ends, Ipswich Town 2, Brentford 0.
Corner,  Brentford. Conceded by Grant Ward.
Nico Yennaris (Brentford) wins a free kick in the attacking half.
Foul by Flynn Downes (Ipswich Town).
Theo Archibald (Brentford) wins a free kick in the attacking half.
Foul by Jonas Knudsen (Ipswich Town).
Substitution, Ipswich Town. Danny M. Rowe replaces Freddie Sears.
Attempt blocked. Romaine Sawyers (Brentford) right footed shot from the left side of the box is blocked. Assisted by Josh Clarke.
Attempt missed. Nico Yennaris (Brentford) right footed shot from outside the box is close, but misses to the left following a corner.
Corner,  Brentford. Conceded by Freddie Sears.
Corner,  Brentford. Conceded by Dominic Iorfa.
Substitution, Ipswich Town. Tristan Nydam replaces David McGoldrick.
Corner,  Ipswich Town. Conceded by Maxime Colin.
Foul by Theo Archibald (Brentford).
Grant Ward (Ipswich Town) wins a free kick in the defensive half.
Myles Kenlock (Ipswich Town) is shown the yellow card for a bad foul.
Theo Archibald (Brentford) wins a free kick on the right wing.
Foul by Myles Kenlock (Ipswich Town).
Substitution, Brentford. Josh Clarke replaces Florian Jozefzoon.
Attempt blocked. Florian Jozefzoon (Brentford) left footed shot from the left side of the box is blocked.
Kamohelo Mokotjo (Brentford) wins a free kick on the right wing.
Foul by David McGoldrick (Ipswich Town).
Substitution, Brentford. Theo Archibald replaces Lasse Vibe because of an injury.
Corner,  Brentford. Conceded by Bartosz Bialkowski.
Attempt missed. Lasse Vibe (Brentford) right footed shot from long range on the right is close, but misses to the right. Assisted by Henrik Dalsgaard.
Attempt saved. Kamohelo Mokotjo (Brentford) right footed shot from outside the box is saved in the bottom left corner. Assisted by Romaine Sawyers.
Maxime Colin (Brentford) wins a free kick in the defensive half.
Foul by Flynn Downes (Ipswich Town).
Substitution, Ipswich Town. Flynn Downes replaces Martyn Waghorn.
Foul by Nico Yennaris (Brentford).
Joe Garner (Ipswich Town) wins a free kick on the left wing.
Delay over. They are ready to continue.
Delay in match Joe Garner (Ipswich Town) because of an injury.
Foul by Harlee Dean (Brentford).
Joe Garner (Ipswich Town) wins a free kick in the attacking half.
Corner,  Brentford. Conceded by Bartosz Bialkowski.
Attempt blocked. Ollie Watkins (Brentford) right footed shot from outside the box is blocked. Assisted by Yoann Barbet.
Substitution, Brentford. Lasse Vibe replaces Neal Maupay.
Corner,  Ipswich Town. Conceded by Maxime Colin.
Ipswich Town made it four wins from four games in the Championship with victory over Brentford at Portman Road.