Sears was born in Brookline, Massachusetts to Alexander Pomeroy and Elizabeth Prescott (Jones) Sears. He received his A.B. in 1903 from Harvard College, followed in 1906 by his B.S. in Landscape Architecture as a member of Harvard's first graduating class in the field. After establishing an office in Providence, Rhode Island, Sears moved to Philadelphia and by 1917 had begun his own practice there, where he remained for the rest of his career.