Newcastle are one victory from the grand final, only 12 months after finishing last on the ladder.
The Knights earned that opportunity by defeating the Warriors 12-10 before a record Eden Park crowd exceeding 48,000.
Dom Young scored early in the second half, while Newcastle's defence protected the narrow advantage and silenced the home supporters.
Coach Justin Holbrook said the result had strengthened his team's belief, although Penrith would provide an even greater challenge next Sunday at Accor Stadium.
"We've got a lot of confidence in the side," Holbrook said. "We've got a lot of self-belief that whoever we're playing, if we play well enough we know we can win.
"We're going to play Penrith with a rest next Sunday afternoon but I'm sitting here confident and can't wait for the game."
Newcastle's defensive resilience has carried them through both finals victories, following a regular season in which their attacking points regularly flowed.
Holbrook built that defensive platform over summer before adding an attacking structure that transformed the Knights into one of the competition's most exciting teams.
There was late concern when captain Kalyn Ponga left the field for a head-injury assessment while Newcastle clung to their two-point margin.
Ponga passed the assessment, avoiding the 11-day standdown period and remaining eligible for the preliminary final.
"It's hard [to reflect on the year] because you're grateful for the win but don't want to sit in that for too long," Ponga said. "You want to get your mind to the next game.
The Knights expect strong support from the Hunter region in Sydney as they pursue an unlikely grand final place.