Educated at St. Mary's College, Rathmines, Dublin, Dean represented Ireland Schools in 1977 and 1978. As a member of St Mary's College RFC 1st XV, he was selected for the Ireland XV against England in 1980 and made his senior Ireland debut against South Africa in Cape Town in 1981.
He was a Triple Crown winner with Ireland in 1982 and 1985 and he played against Wales and Australia at the inaugural Rugby World Cup in 1987.
Dean went on win 32 caps for Ireland between 1981 and 1989, scoring 19 points. He was selected to travel with the British & Irish Lions on the 1989 tour of Australia and featured in the opening match against Western Australia before injury prematurely ended his tour.
Dean is an honorary life member and former past president of St. Mary's College RFC. Following his international rugby career, he set up TopLion Sportswear and spent over two decades working in the sports apparel industry.