Rudi Nierlich's first international success came at the World Junior Championships in February 1984 when he won the gold medal in giant slalom. In the next season he won his first World Cup points after placing 15th in the combined event at Madonna di Campiglio in December 1984, but regularly competed in the Europa Cup. He won the giant slalom title and finished second in the overall event in the 1984-85 Europa Cup. Nierlich repeated his giant slalom win and won the overall title at the 1985-86 Europa Cup before becoming a member of the Austrian senior skiing team in the summer of 1986, earning top 10 finishes in slalom as well as in giant slalom, which qualified him for his first World Championships in 1987. He had little success at that meet, but finished the season with his first podium finish when he placed third in the giant slalom in Sarajevo in March 1987.
The following winter (1987-88) Nierlich won his first World Cup race on his home ground in Schladming in the giant slalom and also finished fifth in that event at the 1988 Olympics. Two more giant slalom wins as well as his first two slalom wins in the next season led him to finish third in the giant slalom World Cup and sixth in the Overall World Cup, but his greatest success came at the 1989 World Championships when he won both the slalom and giant slalom. The following two seasons Nierlich won three more World Cup slaloms, which brought his wins to a total of eight (5 slaloms and 3 giant slaloms). He finished third in the Overall World Cup in 1990-91 and second in the giant slalom World Cup that season and defended his giant slalom title at the 1991 World Championships. He also won two Austrian titles (giant slalom in 1987 and slalom in 1989) and was Austrian sportsman of the year in 1989. Shortly after the end of the 1990-91 season Nierlich died at the young age of 25 in a car accident, when he lost control in the rain and crashed into a wall at high speed.