He was born in Paris. He began practice as an advocate before the parlement of Paris. Dumoulin turned Calvinist, and when the persecution of the Protestants began he went to Germany, where for a long time he taught law at Strasbourg, Besançon and elsewhere. He returned to France in 1557. After writing against the Council of Trent, he was imprisoned by order of the parlement until 1564.
Dumoulin had, in 1552, written Commentaire sur l'édit du roi Henri II sur les petites dates, which was condemned by the Sorbonne, but his Conseil sur le fait du concile de Trente created a still greater stir, and aroused against him both the Catholics and the Calvinists.
It was as a jurist that Dumoulin gained his great reputation, being regarded by his contemporaries as the "prince of jurisconsults". His remarkable erudition and breadth of view had a considerable effect on the subsequent development of French law. He was a bitter enemy of feudalism, which he attacked in his De Feudis (Paris, 1539).
Other important works were his commentaries on the customs of Paris (Paris, 1539, 1554; Frankfort, 1575; Lausanne, 1576), valuable as the only commentary on those in force in 1510, and the Extricatio labyrinthi dividui et individui, a treatise on the law of surety. A collected edition of Dumoulin's works was published in Paris in 1681 (5 vols.).