The 19-year-old agile and technical midfielder joins the Seasiders following a successful trial in Tuesday night's friendly against Redcar Athletic, a fixture which also saw him get his name on the scoresheet, netting Whitby's third in their 9-0 win.
Hailing from Guisborough, Alfie was part of the Boro Academy from the age of nine up until his release this summer.
Towards the latter part of his Middlesbrough career, Doherty spent brief spells out on loan with Hebburn Town and Marske United.
After ten years with Boro, he swaps Rockcliffe Park for the Towbar Express Stadium @ The Turnbull Ground and joins Nathan Haslam's side ahead of the 2023/24 Pitching In Northern Premier League Premier Division campaign.