Doctors and lawyers should ensure that the profit motive does not override their shared calling to public service, urged Chief Justice Sundaresh Menon.
He said those in the "sibling professions" had a duty to mentor the next generation to continue this mission.
"Our calling to practise our arts in a spirit of public service pulls in the contrary direction to the currents that seem to define the present age," he said.
The professional's commitment to learning, excellence and public service can seem strangely out of touch in the present era, which brings unprecedented wealth for some, but also considerable inequality.
But Chief Justice Menon said this "growing sense of inequality" should spur professionals to work even harder for the common good.
His remarks were made as part of the 23rd Gordon Arthur Ransome Oration titled "Law and Medicine: Professions of Honour, Service and Excellence" at the opening ceremony of the 51st Singapore-Malaysia Congress of Medicine. The speech was published last week on the Supreme Court website.
His address outlined some common features shared by both professions, and the greater need for principled and committed professionals in the wake of global changes.
Among other things, he noted that both professions serve members of the public when they are at their most vulnerable, adding that "sickness and lawsuits often come unexpectedly".
He suggested the medical profession could build on its "impressive" pro bono efforts with some centralisation to "help normalise pro bono work" in the minds of new doctors.
His speech also underscored a recurring theme of promoting high professional standards in ethics and competence, to safeguard the interests of laypeople.
Last week, he exhorted new entrants to the Bar to "reflect deeply" on what it means to belong to a profession, echoing what Chief Justice Wee Chong Jin had said in a 1980 speech, where he reminded lawyers that the profession demanded competence, probity, integrity and a devotion to public service.
Chief Justice Wee had also said this duty to public service was under threat in a modern society where success is measured principally in terms of material wealth.
In his speech, Chief Justice Menon said doctors and lawyers, being engaged in front-line efforts to promote health and justice, are bound by the pledges they undertook when first admitted to their professions.
"If we take our oaths seriously, then these cannot be just empty professions," he added, pointing out that the medical and legal communities have much to learn from each other, and much to gain from working together.
"It is a great honour and privilege to be a member of a noble profession; and despite our challenging circumstances, we must fight to ensure that it remains so."