The Reds had been held to draws in the opening two matches of Iraola's reign to spark memories of his start to life at Bournemouth in 2023 where it took 10 matches before he could celebrate a maiden Premier League win.
Isak ensured Iraola did not have to wait as long on Friday nighty with a sixth-minute opener at Portman Road followed by another three minutes later.
Both goals were set up by the excellent Cody Gakpo and, while newly-promoted Ipswich rallied, Liverpool secured all three points.
Iraola handed a debut off the bench to $A231 forward Bradley Barcola in the second half, but the night belonged to Isak as Liverpool moved on to five points from three fixtures ahead of Wednesday's return to Champions League action at home to Atletico Madrid.
This defeat made it two in a row for Ipswich but, after they recovered from their nightmare start, Gary O'Neil's team produced a spirited response and will aim to bounce back at Crystal Palace next week.
Iraola resisted the temptation to start Barcola and then watched Liverpool's big-money signing from last summer immediately wreak havoc in Suffolk.
Only six minutes were on the clock when Gakpo, still at the club despite interest from Tottenham and Manchester City, cut inside and played a defence-splitting pass into Isak, who controlled and rifled a shot beyond Kjell Scherpen.
Scherpen could have got a stronger hand to the effort and three minutes later he conceded again.
Gakpo produced an ever better assist this time with an outstanding outside-of-the-boot through-ball into Isak and the former Newcastle forward squared up Jacob Greaves before he slotted his finish under Scherpen.
The goalkeeper again did not cover himself in glory, but two saves from long-range Dominik Szoboszlai strikes settled down the Dutchman before O'Neil watched the hosts fight back.
First Emersonn was denied by Jeremy Jacquet's block before fine play from Julio Enciso nearly set up a chance for the Ipswich forward, only for full debutant Ronald Araujo to clear.
Leif Davis then sent a header over, but at the other end the offside flag denied Isak a 33-minute hat-trick when he went fractionally too early before converting an excellent Florian Wirtz pass.
Liverpool almost made it 3-0 at the start of the second half when a rapid counter-attack teed up Wirtz, but Daizen Maeda deflected the ball wide.
Alisson Becker spilled an effort by Enciso on the hour mark before Iraola turned to the bench and summoned Barcola in the 64th minute.
Barcola showed his pace moments later in front of Liverpool's noisy away support, but Scherpen raced out to beat him to the ball.
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