Then he flew to Australia and climbed the 7,310-foot Mount Kosciuszko, to cap off his seven-summit conquest.
Strange is a senior in high school who has been climbing mountains since he was 12.
He and his father were expected to be back in Southern California by Wednesday.
Strange broke the previous record set by Samantha Larson of Long Beach. She was 18 when she finished the "seven summits" challenge in 2007.
Strange scaled the original seven summits, which included Everest, Kosciuszko, Vinson Massif in Antarctica, McKinley in Alaska, Aconcagua in South America, Kilimanjaro in Africa and Elbrus in Europe.
The Associated Press contributed to this report.