Their Croatian striker Dino Kresinger and marquee signing Shinji Ono of Japan scored either side of the break to put them in the April 21 final, much to the delight of more than 19,000 partisan supporters at the Parramatta Stadium.
The Central Coast Mariners take on Melbourne Victory in the second semi-final on Sunday.
Unbeaten in their previous 12 matches and having already collected the Premier's Plate by leading the standings at the end of the season, Tony Popovic-coached Sydney took time to gauge their opponents before Kresinger's 16th minute strike signalled their dominance.
A minute earlier the striker had forced the first save of the match from Brisbane goalkeeper Michael Theo.
Sydney maintained their superiority in the second half and their Japanese playmaker Ono sealed the game with a sublime goal when he darted into the box and spectacularly chipped the ball over Theo into the top corer.
Western Sydney will miss Youssouf Hersi in the final after the influential Dutch midfielder picked his second yellow card of the match in the 78th minute.