The Ulsterman ended practice week the fastest rider of all with an unofficial lap record of 135.531mph, with Dunlop also leading the Supersport times in qualifying.
Dunlop was only briefly headed in the four-lap contest, before ultimately winning by 12.3 seconds from Peter Hickman.
The race was delayed by three hours owing to a serious road traffic accident on the mountain this morning, but eventually got away at 2:45pm local time.
David Johnson led the field away on his Jackson Racing Honda, but was quickly overhauled by number two starter Dean Harrison on the Russell Racing Yamaha.
Harrison led by 0.550s from Dunlop through the first sector split at Glen Helen, with Hickman slotting into third.
Dunlop took the lead at Ballaugh Bridge by 1.5s from Harrison, and continued to swell his advantage to 5.4s as he screamed through the start/finish straight on his 600cc MD Racing Yamaha.
Posting a lap of 128.3mph from a standing start, Dunlop threatened to set a new class lap record as he swelled his lead to 13.4s by the end of lap two.
Source: Autosport