Colleen Sostorics began playing hockey in her hometown of Kennedy, Saskatchewan, on the local boys teams until the age of 17. In 1996, she captained her boy's hockey team at the bantam level. She played for Team Saskatchewan at the 1995 Canada Winter Games and the 1997 National Under-18 Championship.
After completing her minor hockey career in Saskatchewan, she accepted an offer to move to attend the University of Calgary, where she played for the women's hockey team. After the 1997–98 season, Sostorics was named to the All-Star Team after the Canada West Championship Tournament.Calgary captured the bronze medal at this tournament.She earned this honour again after the 1998–99 Canada West Championship Tournament. Calgary captured the silver medal at the Canada West Tournament in 1998–99. In addition to the Canada West honours, Sostorics was named a Canadian Interuniversity Athletics Union (CIAU) All-Canadian after both the 1997–98 and 1998–99 seasons. After the 1999–00 Canada West season, Sostorics was named a Canada West Second Team All-Star.
She played for Alberta in the Esso National Women’s Championship and won the Abby Hoffman Cup in 2001, 2003 and 2007.
In 1999, Sostorics made her Team Canada debut with the Under-22 National Team at the 1999 Christmas Cup, winning a gold medal. In 2000 and 2001, she continued to play with the Under-22 team, capturing gold medals at the Nations Cup tournament both years. She served as team captain during the 2000-01 season. Her performance at the Under-22 level earned her a spot on the Senior Women's National team for the 2001 World Women's Hockey Championship.At this tournament, she contributed two goals and an assist as Canada won the gold medal.
In 2002, Sostorics was named to Canada's team for the 2002 Winter Olympics, held in Salt Lake City, Utah. During the tournament, she contributed two assists as Canada took the gold medal. In 2004 and 2005, she also played at the World Championships, winning gold and silver medals respectively.
On September 14, 2010, Hockey Canada announced that Sostorics, along with three other players retired from international hockey.
During her youth, Sostorics competed in soccer and fastball in addition to playing hockey. In 1997, she won provincial championships in all three sports. She was named Most Valuable Player at provincial fastball tournaments in 1994 and 1995.