The Reds dominated possession throughout but could not break the deadlock until the 73rd minute, when Divock Origi picked up on James Milner's flick to finish.
Philippe Coutinho then wrapped up the win for Brendan Rodgers's men six minutes later, the Brazilian finishing off a move from a short corner.
HJK, 21 games into their domestic season, top of the Finnish league and currently competing in the Champions League's qualifying rounds, created few openings in a low-key affair.
Liverpool's final friendly before they begin their Premier League season at Stoke City sees them take on Swindon Town on Sunday.
The visitors - who had 18-year-old midfielder Allan on the bench following his move from Internacional - could have found themselves behind in the sixth minute when Ousman Jallow headed Atomu Tanaka's left-wing corner over the crossbar.
Liverpool had a chance of their own 10 minutes later but Coutinho fired off-target from a tight angle inside the area.
After struggling to make many inroads in the first half, the Reds began the second period brightly as Adam Lallana fizzed a 25-yard effort narrowly wide of the left-hand post.
In the 50th minute, Jordon Ibe drilled in a low ball across the six-yard box which Ings could only divert over the bar under pressure.
Jallow threatened again six minutes later but his effort on the run lacked power and was easily gathered by Simon Mignolet.
Ings glanced a header wide before Lallana saw his shot tipped over as Liverpool pressed hard for a breakthrough
The breakthrough finally arrived when Milner flicked Ibe's cross into the path of Origi, who turned and rifled home, before Coutinho's shot took a kind deflection which diverted the ball into the top-right corner.
