In 1988, aged only 18, Trond Einar Elden had his first international appearance in Nordic combined, finishing ninth at Falun, but 1989 was his greatest year. He surprised everybody at the World Championships in Lahti, easily winning the gold medal two days before his 19th birthday, the youngest ever World Champion in Nordic combined. The next day he won his second gold in the team event, his older brother Bård Jørgen Elden also a member of the team. Trond Einar Elden continued to win, triumphing at both Holmenkollen and Lahti, and ended his fabulous season by being crowned as Junior World Champion in Vang, Norway.
The coming year the V-style in ski jumping became common, and Elden had difficulty adapting to the new technique. He failed completely at the 1991 World Championships, but ended the season strongly with wins in Lahti, Falun and Holmenkollen. He qualified for the 1992 Albertville Games, where he won an Olympic silver medal in the team event. At the 1993 World Championships in Falun he placed third in the individual event and won a silver medal in team. Elden qualified for the 1994 Olympics and the 1995 World Championships, where he had little success, and from 1996 he had problems qualifying for Norwegian teams, missing both the 1997 World Championships and the 1998 Olympic Winter Games in Nagano. He was able to qualify for the 1999 World Championships in Ramsau, where he won another silver medal in the team event. He retired from Nordic combined after the 2000 season, but continued to compete in sprint events in cross-country skiing, and then qualified for the 2002 Winter Olympics and the 2003 World Championships with modest results, although he had two second places in sprint World Cup competitions. Elden ended his active skiing career after the 2005 season. His only Norwegian title in Nordic Combined came in 1989, although he later won five silver and two bronze medals. In 2008 Elden became a cross-country ski coach for the Norwegian Nordic combined team.
Norway