The two Championship clubs have been training at the Fota Island complex near Cork, and the game was played behind closed doors.
Cauley Woodrow and Matt Smith both scored twice for the Cottagers, with their recent signing Sone Aluko on target.
North End manager Simon Grayson used a number of his squad during 90 minutes and looked at different formations.
It was their third friendly of the pre-season programme following 2-1 victories over Bamber Bridge and Chorley at the weekend.
The Lilywhites started in a 3-5-2 system, Bailey Wright, Tom Clarke and Ben Davies playing at the back.
Chris Humphrey and Greg Cunningham filled the wing-back slots, with Alan Browne, Ben Pearson and Daniel Johnson in midfield.
Jermaine Beckford and Joe Garner were paired together in the attack.
Fulham took the lead in the eighth minute, a cross from Ryan Sessegnon headed home by England Under-21 striker Woodrow.
It was Woodrow who doubled the London club’s advantage with 13 minutes on the clock.
Aluko played him through on goal and Woodrow steered a low finish past North End keeper Anders Lindegaard.
Grayson made five changes at the half-hour mark, with Pringle, Paul Gallagher, Paul Huntington, Calum Woods and Mat Hudson joining the action.
Pearson, Johnson, Clarke, Davies and Lindegaard were the men to make way.
Fulham’s third goal came shortly before the interval, a right-wing cross from Floyd Ayite volleyed home by Aluko who joined on a free transfer from Hull City last weekend.
More substitutions at half-time saw Jordan Hugill and Eoin Doyle replace Beckford and Garner.
Two minutes into the second half, Fulham substitute Smith notched his side’s fourth goal, heading in powerfully at the far post from a Stephen Humphrys cross.
Clarke, Davies, Pearson and Johnson were re-introduced after an hour, with Chris Maxwell also coming on.
Fulham completed the scoring eight minutes from time, a shot from Lasse Vigen Christensen hitting Smith and going into the net.
North End are training at Fota Island until the end of the week.