Dunlop opened up TT 2024 with victory in the opening Supersport race of the event to draw level with his late uncle Joey at the top of the all-time winners' list after securing his 26th triumph on the Isle of Man.
He went one better in the first Supertwin contest earlier in the week to become a 27-time TT winner and came into Saturday's delayed Supersport 2 race as favourite.
Shortened to two laps to slot into a busy three-race schedule for the final day of TT 2024 following numerous days of weather disruption, Dunlop led on corrected time from start to finish.
Pushed briefly at the end of the opening lap, Dunlop streaked away on his MD Racing Yamaha across the final tour to add a third win to his scorecar at TT 2024.
Honda's Harrison was his closest challenger in second, while Davey Todd completed the podium aboard his Ducati V2.
Originally scheduled to get under way at 10:30am local time, the second Supersport race of TT 2024 was delayed until 1pm due to rain.
Dunlop led the leaderboards through the first sector split at Glen Helen on the first lap by 0.5 seconds from Todd, who shadowed him in the first Supersport race.
In a tight first sector, James Hillier slotted into third at Glen Helen on the Bournemouth Kawasaki ahead of Harrison.
Dunlop's lead opened up slightly to 0.8s through Ballaugh, with Harrison jumping Hillier on the times in this sector.
Todd continued to bleed time to Dunlop over the rest of the lap, his gap to the MD Racing rider 2.7s at the Bungalow before Harrison leaped into second to end the tour just 0.9s behind the leader.
Harrison's assault on Dunlop's lead was short-lived, though, as the Ulsterman moved 1.7s clear through Glen Helen and opened this up to 3.889s by the time he got to the chequered flag. Dunlop also put in a 129.071mph lap on the second tour.
Todd put on a challenge for second on the final lap, reeling Harrison in to 1.3s through the Ramsey split.
But Harrison pulled 2.343s clear to secure the runner-up spot ahead of Todd.
Jamie Coward finished fourth on his Triumph ahead of Peter Hickman, who told Autosport earlier in the week that he had been battling an 8mph deficit on his Triumph.
Hillier slid to sixth after his early podium charge to beat Mike Browne, Paul Jordan, Michael Evans and Josh Brookes.
