Alloa made it clear from the opening minutes that they intended to take the game to Berwick and Tony Stevenson's perfectly-timed pass on three minutes beat the Berwick offside trap but David McGeown shot wildly over the bar.
Former Alloa player Gareth Hutchison had a chance in the 11th minute to give the visitors the opener but his header from close range was punched clear by Allan Creer in the Alloa goal.
In the 14th minute Ross Hamilton beat the Berwick Rangers offside trap and ran on to a Robert Sloan pass but he failed to capitalise on the chance and his final shot was poor.
Berwick were dealt a severe blow in the 31st minute when former Alloa player Ian Little was stretchered off the field following a collision with Brian McColligan.
This disrupted their style and in reality they never recovered from this.
Alloa were awarded a penalty in the 42nd minute when James Stevenson was pulled down inside the penalty box and Tony Stevenson stepped up to take the pressure kick and slotted the ball past Gary O'Connor in the Berwick goal.
Three minutes later Alloa doubled their lead when Paul McLeod ran on to a McGeown pass and side-footed the ball into the net from 10 yards out.
Alloa made it three after 79 minutes when John Ovenstone out-jumped the Berwick defence to head home a Sloan corner kick.
Ten minutes later from almost the same position he headed home a carbon copy to complete the rout.
Alloa outclassed and outplayed Berwick for most of the match and will go forward to Sunday's second leg with confidence about staying in Division Two for next season.