Gov. Bill Haslam said he doesn't have the votes to veto the measure opposed by scientists and civil libertarians, The (Nashville) Tennessean reported Wednesday.
Haslam said he is concerned the law will create confusion about Tennessee's science curriculum.
"Good legislation should bring clarity and not confusion," Haslam said. "My concern is that this bill has not met this objective."
Passage of the measure by the Tennessee Legislature reopened a decades-old controversy over teaching creationism to schoolchildren.
The law does not require teaching creationism but instead encourages students to question accepted scientific theories such as evolution, the chemical origins of life, global warming and cloning.
The bill protects teachers from punishment if they teach creationism.
Larisa DeSantis, a Vanderbilt University scientist who started a petition drive against the bill, predicted it will bring political controversy into the classroom.