The Honolulu City Council has unanimously passed a bill making it illegal on Oahu to smoke in vehicles while children are inside.
The bill was approved Wednesday and Mayor Kirk Caldwell said he plans to sign it into law.
Those in opposition say the bill intrudes on people's private lives, while backers say those under 18 have no choice but to stay in a vehicle if an adult is smoking.
"We're really concerned for the sake of the keiki who do not have an option as to how they get about," said Lola Irvin, the state's Healthy Hawaii Initiative administrator.
The bill applies to electronic smoking devices as well as tobacco cigarettes.
County and Kauai County have similar laws in place.
Smoking with a minor in a vehicle has been outlawed on Hawaii Island since 2010. On Kauai, smoking with anyone under 13 was outlawed in July 2016. Nine other states or territories across the U.S. also have similar restrictions.