1998-99 was his best season, putting up 18 goals and 33 assists for 51 points; however, Niedermayer was hurt by concussions in the next years and was never able to achieve the same level of scoring ability again.

On July 23, 2001, Niedermayer was traded to the Calgary Flames (alongside a draft pick) in exchange for Valeri Bure and Jason Wiemer.

[5] He and his brother Scott (by this point captain of the Ducks, with Rob as an alternate) won the Stanley Cup together as members of the Anaheim Ducks after defeating the Ottawa Senators four games to one in 2007, becoming the first brothers to win the Stanley Cup together since Duane and Brent Sutter accomplished the feat twice with the New York Islanders in 1982 and 1983.

On September 25, 2009, Niedermayer was signed by the New Jersey Devils, a team his brother Scott played on for 14 NHL seasons.

[7][8][9] Niedermayer was a minority owner of major junior club the Kootenay Ice in the WHL for 18 years before selling his stake (along with brother Scott) to the Chynoweth family after the 2015–16 season.