His first European Tour victory came at the Trophée Lancôme in 1989, when he finished one stroke ahead of Bernhard Langer and José Maríá Olazábal, with his last coming at the 2002 Scottish Open, defeating Freddie Jacobson in a play-off. He became the then-third oldest winner on Tour when he won at Loch Lomond just three days before his 48th birthday.

Romero made a successful transition to the over-50s game in 2004, when, on his first senior start, he finished in a tie for second at The Senior Open at Royal Portrush. His first over-50s title came at the 2005 Travis Perkins Senior Masters at Wentworth, finishing a tournament record eight strokes ahead of Luis Carbonetti and Nick Job.

He successfully defended his Senior Masters title in 2006 and just three weeks later he won his first Senior Major at the Tradition. He also won the 2008 U.S. Senior Open at Broadmoor Golf Club by four strokes from Fred Funk. He won three further times on the PGA TOUR Champions circuit.

Romero won more than 80 tournaments on his home continent of South America and represented Argentina in the World Cup and the Alfred Dunhill Cup on a number of occasions.

Outside of golf, Romero served as mayor of his home city Villa Allende in the province of Córdoba in Argentina. He requested a leave of absence from his position at the end of January 2022 due to health reasons. European Tour