Democrat Jim Kenney overwhelmed business executive and Republican challenger Melissa Murray Bailey in Tuesday's vote. The city hasn't had a Republican mayor since 1952.
Kenney will take office in January. He's replacing Democrat Michael Nutter, who was limited to two four-year terms.
Addressing supporters Tuesday night at Philadelphia's Jewish Museum, Kenney vowed unity.
"Standing in a place that celebrates the aspirations of Jewish families seeking the American Dream, I am reminded of the neighborhood in which I grew up," he said.
"In those days, South Philly was a mix of immigrant families from all different backgrounds and faiths - Irish, Polish, Catholic, and Jewish. But despite their differences, they all worked together to create a better place for their families to live -- whether that meant watching after one another's kids or making sure that the elderly neighbors pavements got shoveled."
Kenney is pushing for universal prekindergarten education. He also wants bail reform in the city, where thousands of people are in jail pending trial.
The city of 1.5 million residents has been on the upswing in recent years. It just hosted Pope Francis and will welcome the Democratic National Convention in July.
But the school system remains troubled, and more than a quarter of residents live in poverty.
Tuesday's candidates included two independents and a socialist.
See real-time results of the election as they come in here.