Rey was born in Buenos Aires and studied acting under Hedwig Schlichter and Milagros de la Vega.

[1] In 1960, he began working with Ana Casares forming the main couple of the television program María Trastorno y yo, but within three months, production had to be interrupted, after he was hired in the United States for a small role in Battle at Bloody Beach.

[2] In 1961, Rey made a guest appearance on the courtroom series Perry Mason as murder victim and title character Vincent Danielli in "The Case of the Injured Innocent".

Rey's best known role was that of casino owner and playboy Carlos Ramirez on the television series The Flying Nun (1967–70), which became an international success.

He played a South American patriot in the Voyage to the Bottom of the Sea episode "The Mist of Silence".

He remained busy on television, playing the role of Karl Duval on Days of Our Lives from 1976 to 1977.

He appeared as part of an ensemble cast in William Peter Blatty's film The Ninth Configuration (1980).