For Cahill, Australia's all time leading goalscorer, it was just his second career hat-trick for the national team, after bagging a treble back in 2004 against Fiji.
The 35 year-old scored in the 6th, 32nd and 37th minutes, and after captain's Mile Jedinak simple goal just before half-time, the Socceroos were cruising up 4-0.
Australia midfielder Aaron Mooy continued his remarkable form, having a hand in three of the four first-half goals.
Fresh off last Thursday's 3-0 win over Kyrgyzstan, the Socceroos started strongly and talisman Cahill opened the scoring in just the 6th minute with a trademark header.
Mooy provided an exquisite free-kick which was met by an unmarked Cahill, who made no mistake from merely a couple of metres out from goal.
Unfortunately for Bangladesh, the 35 year-old was in the mood for more goals and he only had to wait until the 32nd minute to bag his brace, albeit in scrappy fashion.
Cahill produced some improvisation to kick the ball into the ground and then clear the hosts' goalkeeper, after also negating three defenders.
But he wasn't finished there, and just five minutes later after he had his hat-trick after finishing some great lead-up work from Mooy down the left, to make it 3-0.
When unmarked Socceroos captain Jedinak nodded home at the back post in the 43rd minute, again off a Mooy free-kick, the match was effectively over at the break.
With the match essentially wraped up, Australia coach Ange Postecoglou had the luxury of taking Mooy and Massimo Luongo off at half-time, and replacing them with James Troisi and Tommy Oar.
While Bangladesh produced a more-spirited performance during the second-stanza, the damage had already been done as the Socceroos settled for a 4-0 win and moved to top place in their qualifying group, prior to Jordan's clash with Kyrgyzstan later on Wednesday morning.
Australia 4 (Cahill 6', 32', 37', Jedinak 43')
Bangabandhu National Stadium, Dhaka, Bangladesh