A try from fly-half Jonathan Sexton - and another Leigh Halfpenny conversion - put the Lions clear again heading into the final quarter.
Sexton touched down after receiving the final pass from Halfpenny in a slick Lions move in the left corner.
Australia had closed the gap to just three points early in the second half through two Christian Leali'ifano penalties.
Halfpenny added another penalty of his own.
More top news
A mild night ahead with mist and hill fog.
In week two of the brand new series of The Voice on ITV a Welsh artist stole the show for the second time!
The council plans to turn the building into what they're describing as a 'cultural hub'.