Hailing from Banteer, County Cork, Dunbar joined local amateur team O'Leary Stone Kanturk in 2013.

These include two general classification victories, three stage wins and a national time trial championship.

Approaching the finish in a group of fourteen riders, he sprinted clear with one kilometre to go and held on to win the stage ahead of Quinten Hermans and Max Poole.

[13] He took his first general classification win at the 2022 Settimana Internazionale di Coppi e Bartali, a five-stage race in Italy.

Raced on a 36.6km course around Athea, Dunbar finished 15 seconds ahead of Ryan Mullen to take his first elite national title.

[16] His first professional win came at the 2016 An Post Rás representing American team Axeon Hagens Berman.

[18] Dunbar finished the race ahead of future Grand Tour winners Jai Hindley and Sepp Kuss.

His second appearance at one of cycling's showpiece three-week races came at the Giro in 2023, taking five top-ten stage results on his way to seventh place overall.