Wales marked their return to a major football tournament since 1958 with a win after defeating Slovakia 2-1 in the Group B opening game in Bordeaux on Saturday.
Gareth Bale put Wales 1-0 up in the 10th minute, converting a superb free-kick.
In the 61st minute, substitute Ondrej Duda equalised for Slovakia to make it 1-1.
But with nine minutes remaining, Hal Robson-Kanu scored Wales second to earn them the win.
Wales' next game is against England billed for Thursday.
Slovakia will try to bounce back from the loss to Wales when they take on Russia on Wednesday.