At a pitch inspection at 3.30, it was decided the pitch was not suitable for playing rugby after heavy rain had fallen trhoughout the day in the Welsh capital.
The Ospreys, referred to as the Eyasses, booked their place in the final with a 12-10 win over the Scarlets a fortnight ago, wing Jordan Adderley scoring two tries.
Blues North earned their spot in the final after an emphatic 41-5 win over Blues North in challenging weather conditions at the end of last month.
It is the fifth time that the young Ospreys have reached the final at U16 level, having appeared in four of the previous seven, winning all four matches.
Admission to the game is FREE so fans are urged to turn up and support the youngsters at Cardiff Arms Park
