Two minutes into injury-time in Sunday's Scottish First Division clash, Andreu fired home from the edge of the box to stun the hosts who had Darren Dods sent off late in the game.
Stewart Murdoch had given the Bairns a 34th-minute lead from the penalty spot after David Weatherston was fouled by Paul Watson.
However, six minutes before the break the visitors were level through Callum Fordyce who headed home Andreu's corner.
But nine minutes later, Livingston were reduced to 10 men when Watson was shown a straight red for slicing down Andy Haworth.
Dods also saw red on 88 when he collected his second yellow card of the afternoon for hauling back Iain Russell and Andreu sealed three away points a few minutes later.