The Ballymoney rider added to his haul of three after fending off Bruce Anstey in Wednesday's Supersport race.
As Dunlop blasted his way around on a final lap he smashed his own race record set on Monday.
He also managed a lap record of 128.667 mph.
It's now four wins for the rider who hopes to make it five on Friday when he races in the Lightweight and Senior events.
Earlier in the week, Dunlop took both the Supersport and Superstock races on Monday.
Michael managed a time of 1:10:37 in the Superstock race - finishing 16 seconds ahead of second place rival Gary Johnson.
He was also joined by his brother on the podium for the Supersport event - with William Dunlop taking third place 23 seconds behind his sibling.
Those wins brought Dunlop's TT haul to six - surpassing his late father Robert's five victories.
A winner out on the course at his first attempt Robert Dunlop took the 1983 Newcomers 350cc race.
After a long career at the TT, he was killed during a practice race at the North West 200 in 2008.
On Sunday, son Michael clocked his first 'big bike' Isle of Man TT win taking the Superbike race.
He enjoyed a huge 41-second lead on his Honda Fireblade as he powered home to victory.
Dunlop secured the win over Cameron Donald - who finished second with a time of 01:46:10.
John McGuinness finished a further 41 seconds behind Donald.
Michael Dunlop completed the six lap race clocking an average speed of 128.7 mph.
Sunday's win came 30 years after his uncle - legendary Ballymoney rider Joey Dunlop - landed his first win around the course on Honda machinery.
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