The company said it would now accelerate construction, ensuring Honeymoon remained on track for first production in the final quarter of 2023.
It expected to steadily ramp up production to 2.45 million pounds a year within three years.
The redevelopment is fully funded after Boss recently raised $125 million through a share placement and share purchase plan.
"This final investment decision puts Boss firmly on track to be Australia's next uranium producer," managing director Duncan Craib said.
"We are fully funded with no debt, fully permitted and extensive infrastructure in place.
"Our front-end engineering studies are completed and we are ready to order key equipment and start construction immediately.
"This puts us in an extremely strong negotiating position with utilities and ensures we can capitalise on the looming uranium supply deficit."
In earlier announcements, Boss said it would hire 80 to 100 people for the Honeymoon operations and confirmed on Wednesday it already had a highly-experienced senior project management team in place.
The mine, about 80km northwest of Broken Hill, is expected to have an initial life of 11 years, though that could be extended through nearby satellite deposits.
It previously operated from 2011 to 2013 and Boss bought it in 2015 from Uranium One for $9 million.
There are currently three uranium mines in production in Australia, according to the World Nuclear Association: Ranger mine in NT, which is processing stockpiled ore; BHP's Olympic Dam mine in SA; and the Beverley mine, also in SA.
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