Chris Iwelumo was the star man, enjoying the best night of his life as he rammed home four goals.
He even found time to set up the other goal for his fellow striker Jamie Cureton.
Hull were simply blown away in a one-sided second half and they can have no complaints as they remain deep in relegation trouble.
Parkinson was the darling of Layer Road when he guided Colchester to promotion into the Championship for the first time in the club's history last May.
But he incensed many Colchester fans for his shock departure to Championship rivals Hull a matter of weeks later.
And the Layer Road faithful took great delight in taunting their old manager throughout the evening, as well as chanting the name of their new manager Geraint Williams.
Hull, who are second from bottom, actually took the lead in the 16th minute when Colchester old boy Craig Fagan flicked on for veteran striker Nicky Forster to bundle home at the far post.
But that was the extent of Hull's joy. Colchester were level just three minutes later thanks to Iwelumo's pin-point header from Kevin McLeod's excellent free-kick.
There wasn't much to choose between the two teams during the first half, but that all changed after the break.
The U's took the lead in the 54th minute when defender Danny Coles brought down Iwelumo in the box. The big Scotsman clambered to his feet to convert the penalty.
Four minutes later and Hull were trailing by two goals when Iwelumo flicked on for Cureton to sweep home his tenth goal of the campaign. However, defender Michael Turner should really have cleared the danger before the ball even got to Cureton.
The game was over as a contest but it was just starting for Iwelumo. He completed his hat-trick by firing home a shot on the turn in the 66th minute after skipper Karl Duguid's first shot had been well blocked by the keeper Boaz Myhill.
The rout was completed in the 80th minute with Iwelumo chalking up his fourth goal of the night.
Johnnie Jackson's shot was cleared off the line by Turner, while keeper Myhill palmed away the follow-up from George Elokobi but Iwelumo was in the right place to bury the loose ball.