The World Wide Fund for Nature encouraged people, cities, businesses and landmarks to turn lights off at 8:30 p.m. PT.
Hong Kong embraced Earth Hour and participated this year.
Locally, Earth Hour was observed at Los Angeles City Hall, the Los Angeles International Airport gateway pylons and Los Angeles Mayor Eric Garcetti's residence.
The mayor called on residents to take part in the observance.
"Reducing energy consumption reduces pollution and the strain on our utility infrastructure," Garcetti said. "While it will take more than an hour to solve climate change, by joining this movement we send a strong message that Angelenos care about the health of their city, their environment and the globe."
The Santa Monica Pier's Ferris wheel and Manhattan Beach pier also shut off its lights, and Staples Center switched to green lights.
CNS contributed to this report.
