On 8 January 2011, Alfei made his professional debut for Swansea City in a 4–0 victory against Colchester United in the FA Cup, where he was named man of the match. Alfei made his league debut a week later, as an 88th minute substitute against Crystal Palace. Alfei also played in Swansea' FA Cup fourth round tie against Leyton Orient in 2011, Alfei played the whole match. He signed a new three-year contract in April 2011.


Alfei represented and captained the Wales under-19 team and has played several times for the Wales under-21 team. In January 2013 he was selected in the Wales under 21 squad for the friendly match against Iceland on 6 February 2013.

On 9 May 2013, Alfei signed a new contract with Swansea until June 2016 and recently spent time on loan with Northampton Town FC.