The company had been seeking $15 million, but the syndicate of underwriters, led by PI Financial Corp, exercised an overallotment option.
New shares were issued at 70c, equal to Friday's closing price.
The proceeds will be used to advance the Plutonic gold mine in Western Australia, to repurchase a royalty from former owner and major shareholder Northern Star Resources, and for working capital.
"The strengthening of our balance sheet allows the company to execute on its strategy of increasing production and cash flow from its Plutonic gold operations," Superior interim CEO Tamara Brown said.
"We are very pleased to be in a position to exercise our option to repurchase the Northern Star royalty, significantly improving our projected cashflow over the next two years.
"We will also continue to advance underground development, accelerate our exploration plans to follow up on our recent drilling success1 and complete a preliminary economic assessment of a pushback at the Plutonic main open pit."
Superior had $15.6 million cash at the end of the June quarter.
The underperformance of Plutonic, which produced 15,177 ounces at all-in sustaining costs of US$1547 an ounce in the June quarter, resulted in the departure of founder and CEO Chris Bradbrook.
Superior has initiated a strategic process, which could result in a sale or joint venture.
The company has a market capitalisation of C$68 million.
