Born in Leiden, South Holland, Opdam began his professional career with AZ Alkmaar, being relegated to the second division in his first year and immediately promoting back in the following.

After a 3–3 draw in Istanbul, the Turkish led 2–0 at half-time, and the defender headed home from a Julian Jenner free kick with seven minutes to go, making it 2–2 and sending his team to the next round on away goals rule (eventually reaching the last-eight stage);[1] in the 2004–05 edition AZ reached the semifinals of the competition, the second time in 24 years.

In 2008, one year after finishing second in the Dutch Cup, 32-year-old Opdam had his first abroad experience, signing for Austrian club FC Red Bull Salzburg.

After two seasons, being an important defensive unit in the conquest of back-to-back national championships, he returned to his country, joining FC Volendam in the second level.

Opdam would be, however, overlooked by national team coach Marco van Basten for the final stages in Germany, gaining a total of eight caps.