For the first six months of the previous financial year, Optus had recorded a profit of $235 million.
The company said in a statement that operating revenue had falled 9% to $4.1 billion while EBITDA declined to $997 million.
"In the half year, operating revenue decreased 9% to A$4,064 million and EBITDA declinedto A$997 million.
It added that these headwinds were exacerbated by the impact of the pandemic, with revenue from its mobile services falling 2%, with customer growth, roaming and pre-paid revenues all hit by the lockdown and the ban on international travel.
Optus said excluding the effects of the pandemic, mobile service revenue showed low single-digit growth. Fixed NBN customers grew by 235,000 from a year earlier and accounted for 90% of the company's fixed broadband base as of 30 September.
Revenue grew for Optus Enterprise and ICT services revenue increased strongly.
Optus chief executive Kelly Bayer Rosmarin said: “Optus has been focused on doing the right thing to support customers and staff during a very challenging year, and our results reflect the conditions we currently face.
"I take heart from the inherent resilience in our core business, and the strong recoveries we have seen across our channels with the easing of COVID-19 related restrictions. Our customer satisfaction has never been stronger, our complaints are reducing, and our offering is very compelling and provides great value for customers.
"While the headwinds are likely to continue to dampen our performance for the foreseeable future, I am optimistic about our longer term plans and expect a return to growth underpinned by a continued focus on customers."