The 1911 Isle of Man TT was the first time the Junior TT race took place and was open to 300cc single-cylinder and 340cc twin cylinder motor-cycles and was contested over 5 laps of the new 37.5 mile Mountain Course. The first event on the new course was the Junior TT Race and was contested by 35 entrants. It was won by Percy J. Evans riding a Humber motor-cycle in 3 hours, 37 minutes and 7 seconds at an average speed of 41.45 mph.
The 1912 event was the first to limit the Junior TT to only 350 cc machines and this engine capacity prevailed until 1994.
The lap record for the Junior TT is 17 minutes and 35.659 seconds, at an average speed of 128.666 mph (207.068 km/h) set by Michael Dunlop on lap 2 of the 2013 Isle of Man TT 600cc Supersport Junior TT Race 2. The race record for the Junior TT is 1 hour, 11 minutes and 36.808 seconds at an average race speed of 126.445 mph (203.494 km/h) set by Ian Hutchinson during the 2016 600cc Supersport TT Race 1.