Garcetti, speaking in English and Spanish, told a crowd of hundreds at the signing event that he wanted to lift the city's lowest-paid workers out of poverty.

"Too many Angelenos have been left behind even as we've put the recession in the rearview mirror," he told union representatives, immigration and minority activists at the ceremony.

The Los Angeles City Council approved the wage hike in May with a 14-1 vote. The law requires businesses with 25 or more employees to increase pay for minimum wage workers to $15 by 2020.

The pay hikes start in July 2016 with a jump to $10.50. Smaller businesses will have an extra year to meet the new minimums.

Opponents say the law will place an unfair burden on small businesses and will drive employers away from the city.

Addressing those concerns, Garcetti said: "We would not have done this if we believed this would hurt our economy."

The city council included in the law a stipulation that the city's minimum wage should continue to increase based on the Consumer Price Index starting in 2022.

The legislation also included a $500,000 budget to establish an Office of Labor Standards. It will investigate whether businesses in the city are paying workers fairly.

The federal minimum wage has been $7.25 since 2009. Other U.S. cities such as Seattle and San Francisco have increased minimum wages in recent years.

The new law will impact an estimated 600,000 workers in Los Angeles, the second-largest U.S. city.

"The winds of this country blow from West to East," Los Angeles City Council President Herb Wesson said at the event. "Don't believe people across the country are not watching this."

The city council in September approved a pay increase for hotel workers to $15.37 an hour.