Gustin saw off competition from actors including James Mackay ('Singularity') and Matt Barr ('Hatfields & McCoys') for the role, reported Variety.
The 23-year-old actor will debut on The CW's 'Arrow', appearing in three episodes, starting with the eighth and ninth of the new season, with the 20th designed to serve as a backdoor pilot to launch a new superhero show for the network.
'Arrow' star Stephen Amell congratulated Gustin via Twitter as did co-star Colton Haynes, another recent addition to the series.