The visitors, with the wind advantage, dominated the first half and two goals from Kenny Feeney helped them to a 2-8 to 1-7 interval lead. Jonathan O’Neill netted for Wicklow.
Then came O’Brien’s devastating hat-trick, which was completed in the 67minute when he cheekily batted a cross from Eamonn Kearns to the net from close range.
Meanwhile, Down beat Armagh 1-20 to 1-11.
Scorers for Wicklow: A O’Brien 3-10 (one free), J O’Neill 1-3, J Henderson 0-1, S Kelly 0-1, R Keddy 0-1, E Kearns 0-1, G Bermingham 0-1, C Moorehouse 0-1.
Scorers for Mayo: K Feeney 3-3, S Regan 0-3, S Hoban 0-1, D McTigue 0-1, D Gallagher 0-1, B Hunt 0-1.
WICKLOW: J Murphy; J Connors, B Osbourne, B Cuddihy; G Bermingham, L Kennedy, E Dunne; S Kelly, R Keddy; J Henderson, E Kearns, M Lee; E Glynn, J O’Neill, A O’Brien.
Subs: R Byrne for J Connors, C Moorehouse for E Glynn, G Byrne for M Lee, G Weir for J O’Neill, S McGrath for E Dunne.
KILDARE: D O’Brien; A Brennan, A Connolly, B Hunt; S Morley, P O’Flynn, C Charlton; S Markham, N O’Malley; S Hoban, D McDonnell, K Feeney; D McTigue, S Regan, D Gallagher.
Subs: F Lyons for S Markham, D Horan for D Gallagher, G Nolan for N O’Malley.
Referee: P O’Dwyer, Carlow.