They were originally due to play the venue in 2020 and then again last year, and the Irish pop act didn't disappoint when they finally arrived on stage.
Westlife mania was in town as the foursome - Nicky Byrne, Kian Egan, Mark Feehily and Shane Filan - performed hit after hit from their back catalogue.
Opener Starlight, from their latest album Wild Dreams, was followed by the Billy Joel cover Uptown Girl, and then a string of hits.
When You're Looking Like That, If I Let You Go, Fool Again, Swear It Again, World Of Our Own, What About Now and Flying WIthout Wings were punctuated with crowd pleasers such as Mandy and a nine-song Abba medley, before the show closed with Hello My Love and the rousing You Raise Me Up.
Support came from bluesy rock and soul artist Kevin Davy White, who came third on The X Factor in 2017.
Summer 2022 continues at Scarborough OAT on Tuesday with Welsh legend Tom Jones.
1. Westlife wow the OAT
Westlife at Scarborough's Open Air Theatre. Photo courtesy of Cuffe and Taylor.
2. Westlife wow the OAT
Westlife at Scarborough's Open Air Theatre. Photo courtesy of Cuffe and Taylor.
3. Westlife wow the OAT
Westlife at Scarborough's Open Air Theatre. Photo courtesy of Cuffe and Taylor.
4. Westlife wow the OAT
Westlife at Scarborough's Open Air Theatre. Photo by Steve Bambridge.