Robin van Persie finished off a neat move before halftime to give the Dutch the lead but Cameroon levelled ealry in the second half through Samuel Eto'o's penalty.
Huntelaar fired home winner in the 83rd minute, scoring fron a rebound after Arjen Robben hit the post with a 20-yard drive
The Netherlands will face Slovakia on Monday for a place in the quarter-finals.
Group E Final Standings
Group E W D L F A GD Pts Netherlands 3-0-0 5:1 +4 9 Japan 2-0-1 4:2 +2 6 Denmark 1-0-2 3:6 -3 3 Cameroon 0-0-3 2:5 -3 0