The State senate approved the bill mandating greenhouse gas emissions disclosure last week, leaving Newsom with the final say.
Asked at the start of "Climate Week" in New York, a week of events coinciding with the U.N. General Assembly, whether he would sign the bill, Newsom replied: "Of course I will sign that bill."
"We have some cleanup on some little language," he added, without giving details.
Newsom acknowledged there had been "a lot of opposition" to the bill which would require companies earning more than $1 billion a year and operating in the state to measure categories of emissions including a complex category linked to supply chains and end-users, known as Scope 3.
The Securities and Exchange Commission is yet to issue its own guidance.
Multinational companies including Apple (AAPL.O) and Microsoft (MSFT.O) have voiced support for the bill, but the California Chamber of Commerce said it would increase costs and paperwork for firms.
Measures aimed at managing environmental, social and governance (ESG)factors have created controversy among U.S. politicians in recent years. Lawyers have said the new California legislation could still be challenged in court.
Last week, California sued major oil companies, alleging they had played down the risks posed by fossil fuels.
