Some of the boats burned through the lines tying them to the dock and floated freely, threatening to spread damage, San Bernardino County fire authorities said in a social media post.
Crews used a fire boat to hose down the flames and corral the boats. The dock also sustained major damage before the flames were knocked down.
A hazardous materials team also responded because of the possibility that fluids and other hazards might affect the lake.
Lake Arrowhead is a scenic tourist destination high in the San Bernardino Mountains east of Los Angeles.