The world number four will be joined by fellow former Queen's champion Marin Cilic who has also confirmed he will sharpen his grasscourt game on the west London lawns.
Dimitrov, who won the ATP World Tour Finals in London in November, the biggest title of his career, won the Queen's crown in 2014 and went to reach the Wimbledon semi-finals.
"The Queen's Club Championships is one of my favourite tournaments, there's so much history at the event and grass is one of the best times of the year," Dimitrov said.
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"Now that I have the 02 title, I am motivated to do even better at Queen's and Wimbledon this year."
Cilic lost in the Queen's final last year to Feliciano Lopez and in the Wimbledon final to Roger Federer. He again fell one victory short at this year's Australian Open, losing to Federer in a five-set final.
World number two Rafa Nadal has also confirmed he will play at Queen's and Britain's Andy Murray, recovering from hip surgery, could also play in the tournament he has won five times.
(Reporting by Martyn Herman, editing by Ed Osmond)
