Vieira has accepted a deal which will could keep him in Genoa until 2023 following a successful medical earlier today.
Sampdoria agreed a fee in the region of £7m with Leeds yesterday and the Elland Road club have opted to cash in on Vieira despite the early promise shown by the England Under-21 international.
Vieira made a dramatic breakthrough during the 2016-17 season, his first as a professional, but has paid for a disappointing second campaign and his failure to force his way to the front of the plans of head coach Marcelo Bielsa this summer.
The 20-year-old flew into Genoa last night and completed formalities with Sampdoria in time to travel back to England with their squad for forthcoming friendlies against Watford and Fulham. Sampdoria’s official Instagram account showed him arriving at Farnborough airport with the rest of their players this evening.
Sampdoria, under head coach Marco Giampaolo, finished 10th in Serie A last season.
Vieira’s exit from Elland Road is due to be confirmed shortly, ending his career there after 60 first-team appearances.
The Guinea Bissau-born midfielder came to Leeds on a scholarship deal by way of a spells with Benfica and the i2i academy. He turned professional in May 2016.