Josefin made her debut for the national team at the World Championships in Rio de Janeiro in 1995 and has since taken 43 medals in international championships, including the individual World Championship gold, silver, bronze and three European Championship gold. In relay contexts, Josefin has participated in teams wich has won many medals in both the World Championship and Europeen Championships.
She concider the gold medal that she won in the 200m freestyle World Cup in Indianapolis in 2004 is her greatest success. She also swam on the team who won Olympic bronze in the 4 x 100 m free at the Sydney Olympics.