Flowers was Dowie's assistant at Coventry for a year so the pair know each other well.
Tim told the club's website: "I am delighted to be here to assist Iain.
"I like the look of this squad, I've seen QPR play a few times over the last 12 months, and I am very optimistic about next season."
He added: "A squad as talented as this one, with a few new additions added to the mix, can certainly go a long way."