The staged development will increase production from the current rate of about 62,000 ounces of gold per annum to 100,000-120,000ozpa by this time next year.
This will be implemented using the current, recently refurbished crushing circuit, the previously expanded mill circuit and a new 750,000 tonne per annum concentrator.
GR Engineering Services has been awarded the $25.7 million engineering, procurement and construction contract for stage one works, which will begin in early December.
Wiluna will fund the expansion via existing cash of about $15 million, operating cashflow and the $40 million tranche two of a debt package with Mercuria.
In the meantime, studies continue on a stage two expansion to take production to about 250,000ozpa by late 2023/early 2024.
"The challenge now is to deliver on stage one and scope out the optimum size for stage two given the considerable size of the Wiluna orebody," Wiluna executive chairman Milan Jerkovic said.
"We are now exactly halfway through our 24 months strategy to turn the Company around, deliver real value to our shareholders and maximise the true potential of the Wiluna Mining Complex. We are delivering on our promises and we plan to execute with precision."
Earlier this week, the company upgraded resources for Wiluna to 7.3 million ounces at 1.6 grams per tonne gold.
"The sheer size of Wiluna, which is now the seventh-largest gold district under single ownership in Australia, based on JORC mineral resources, throws up challenges but nothing worthwhile comes easy, and we believe the prize for shareholders of developing this project in a systematic, thorough and staged manner to become a tier one asset in a tier one jurisdiction will be worth it," Jerkovic said.
Shares in Wiluna were up 3.1% to $1.815. The stock started August at $1.25.