NSW Premier Dominic Perrottet is now considering whether the minister breached the ministerial code of conduct by owning the shares, he said.
Transurban revealed it collected a staggering $835 million in tolls from Sydney drivers over the past six months earlier this month, making total record earnings of $1.66 billion for the six months ending December 31.
Damien Tudehope told reporters he had not known about the shares, which had been within a "diversified" fund in his superannuation.
While he presented letters to the premier disclosing the fund, he said he wasn't aware of the Transurban shareholding until a journalist contacted him earlier this week.
He had been involved in government discussions involving Transurban during his time in cabinet.
"I didn't know about the holding of the shares, and I'm aware there was a profit made and I've given an assurance to the premier, I will donate any profit ... to charity," the minister said in a snap press conference.
The shares had increased in value by about $6000 since he entered the parliament in 2014.
The shares were sold Friday morning, he said.
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