Born in Brazzaville on 15 November 1911, he was the son of the Governor-General of French Equatorial Africa, Martial Henri Merlin.

Merlin first represented the France Davis Cup team in the final of the 1933 tournament, against Great Britain at the Stade de Roland Garros.

France, under The Four Musketeers, had won the previous six tournaments, but were an ageing side and brought in Merlin to counter the younger British players.

He had a win over fifth seed Henner Henkel en route to the quarter-final defeat in which he took countryman Christian Boussus to five sets.

After the war, Merlin made one final appearance at his home tournament, at the 1947 French Championships, but ended up defaulting his opening match.