The Scotland international, 24, put the visitors in front inside four minutes after latching on to Rudy Gestede's flick-on off a long ball.
He outpaced Huddersfield defender Murray Wallace, drew keeper Alex Smithies and fired low into the bottom left corner.
Rhodes left Town in August 2012 for a club record £8million - becoming in the process Blackburn's most expensive player.
The Oldham-born striker had three prolific seasons at the Terriers and has been no less impressive for Rovers.
He came into this contest having netted 17 times and cemented his place as Blackburn's top scorer with a treble.
Rhodes struck again on 55 minutes by heading in off the post from Craig Conway's cross after good work by veteran David Dunn.
Blackburn went 3-1 up on 65 minutes thanks to a blunder from Smithies, who left a Conway shot slip through his hands. Rhodes though was not done.
He pounced on a mistake by Adam Clayton to net his 20th goal of the season and second hat-trick for Rovers.
Huddersfield midfielder Clayton slipped, with Rhodes clinically stealing the ball and going on to beat Smithies in a one-on-one.
Rovers boss Gary Bowyer held crisis talks with his players following defeats to Bolton, Burnley and Bournemouth.
It clearly had an effect as the side was even able to shrug off injuries to Jason Lowe and Gestede on the road to victory.
Lowe had to be taken off on 26 minutes and soon after Frenchman Gestede was rushed to hospital as a precaution.
He was involved in a clash of heads with Town skipper Peter Clarke and was carried off in a head brace to a waiting ambulance.
The injuries led to nine minutes of stoppage time in the first half, though by then Huddersfield were level at 1-1.
Adam Hammill's low cross on 25 minutes went through a crowd of players and sneaked in at the far post.
It came about after Paul Dixon was fouled by Lee Williamson. Clayton played the ball down the left channel for Hammill to run on to.
Thanks to Rhodes and Conway the home side fell 3-1 down and at that stage boss Mark Robins made a double change.
He brought on winger Sean Scannell and fit-again striker James Vaughan, making his first in five games due to a calf injury.
They had an immediate impact by creating the opening on 71 minutes for Nahki Wells to end his goal drought with a low drilled shot.
Wells, Town's record £1.3m signing from Bradford, had not scored in nine matches before today.
Town piled on the pressure in the search for an equaliser, with Danny Ward missing an open goal after keeper Paul Robinson denied Wells.
But then against the run of play Clayton's mistake let the predatory Rhodes in to seal victory. All three goals were celebrated by Rhodes in muted fashion, perhaps as a sign of respect for his former club.