In 1965, while living in Los Angeles. he founded the Manatt law firm with his long-time friend and colleague Thomas Phelps, a banking and finance attorney. He began his legal career focusing on banking and financial services. In 1976, Mickey Kantor joined the firm and his name was added to the letterhead, until his departure in 1993. L. Lee Phillips, an entertainment lawyer, joined the firm in 1977, and became a named partner soon after. For its founding location, the firm headquarters are in Los Angeles. Over time, offices were opened in 8 different cities, primarily in California but also in New York and Washington D.C.