Niklas Edin participated in as many as ten different sports simultaneously before he took up curling. He started curling in 1999, inspired in part by the Swedish women's team skipped by Elisabet Gustafson when they secured the bronze medal at the 1998 Winter Olympics. Five years later in 2004, Edin skipped his own team to a World Junior Curling Championship title for Sweden, defeating the team skipped by Stefan Rindlisbacher for Switzerland. The following year, Edin was selected as the alternate for the silver medal-winning Swedish team skipped by Nils Carlsén at the World Junior Curling Championships. Edin also skipped a new team in 2005 to a silver medal at the European Mixed Curling Championships, together with future longtime teammate Sebastian Kraupp. In 2006, Edin won a second silver medal at the World Junior Curling Championships, this time playing third for Team Carlsén. The team also qualified for the 2006 World Men's Curling Championship, finishing in fifth place.