Kyle Lafferty made it 3-0 to the hosts 11 minutes after the break.
The visitors made the score a little more respectable with a consolation goal just a minute before the final whistle.
Fulham defender Chris Baird skippered the side for the first time and he praised the impact that new manager Nigel Worthington had given the squad.
"The boys have taken on board the rules and ideas Nigel has - he's big on discipline and it's sunk in already with the players," said Baird.
"It showed in this game - we're sticking together as a team and we are giving the performances still.
"We've got two tough away games coming up but we know we can get six points and push on for qualification."
Northern Ireland: Taylor, Duff, Baird, Craigan, McCartney, Gillespie, Clingan, Davis, Brunt, Healy, Lafferty.
Liechtenstein: Jehle, Michael Stocklasa, Martin Stocklasa, Telser, D'Elia, Polverino, Ronny Buchel, Daniel Frick, Biedermann, Rohrer, Mario Frick.