The duo combined for a 135-run partnership as the hosts ended the weather-effected day on 147/2 at the iconic Sydney Cricket Ground.
After perusing the dry surface at a ground that favours the tweakers, Australian captain Pat Cummins was delighted to win the crucial toss and elect to bat.
But it would be tourists who struck the first blow via paceman Anrich Nortje. The 'tache-donning seamer hit a good length outside off stump and David Warner flashed at it, which was only enough to get a thick outside edge. Claimed comfortably by Marco Jansen at slip, the strike had the hosts 12/1.
However, the imperious Labuschagne and Khawaja would see off the quicks and pile on the runs over the next hours, forcing the spinners, Keshav Maharaj and Simon Harmer, into play.
They toiled unsuccessfully in the sun, with Harmer providing the only near-breakthrough with an overturned lbw involving Khawaja.
Again, there appeared to be a moment of respite when lanky-left armer Jansen nicked off Labuschagne, on 70, to first slip where Harmer claimed the low catch. Unsurprisingly, Labuschagne stood his ground while the onfield umpires gave 'out' on the soft signal.
However, the South African-born batter continued to live a charmed life in his Test whites, as third umpire Richard Kettleborough overturned the decision.
Bad light stopped play - and Australia's rampant run rate - for two hours with the Baggy Greens at 138/1.
When play resumed late in the afternoon, never-say-die Nortje produced some sharp bounce to catch Labuschagne by surprise, knicking it through to the waiting gloves of Kyle Verreynne.
The players were then taken again off as mizzle circled the ground, with most of the Sydney faithful already out the gates.