He was born at the Manor of Queens Village on Long Island, New York to Henry Lloyd and Rebecca Nelson.

James apprenticed and studied under the Boston physicians Silvester Gardiner and John Clark between 1745 and 1748, and, in 1749, traveled to London to work as a resident at Guy's Hospital.

[1] There, he learned groundbreaking surgical techniques like flap amputations, and attended lectures performed by pioneering surgeons and obstetricians.

[3] After completing his tenure in London, Lloyd returned to Boston, where, in addition to opening his own practice in surgery and obstetrics, he showed a commitment to educating a new generation of physicians.

[5] At the outbreak of the Revolutionary War, Lloyd was serving as a surgeon for a British military unit based near Boston.