After 70 minutes of drab fare at Dobsonville Stadium in this vast township south west of Johannesburg, the game sprang to life as Nigeria took a two-goal lead only to surrender it.
Goals from Olanrewaju Kayode and Uche Nwofor rocked Cameroon, who won a group match between the countries and kept three clean sheets in four matches en route to the decider.
But the 'Indomitable Cubs' lived up to their nickname by refusing to accept defeat and Franck Ohandza and Edgar Sally scored within four minutes to force 30 additional minutes.
The 'Flying Eagles' regained the lead two minutes into extra time through Terry Envoh, whose first goal of the biennial two-week tournament proved decisive.
After winning four consecutive championships in the 1980s, Nigeria had to wait until 2005 for their fifth success in a competition restricted to under-20 footballers.
The third place play-off also saw a group result reversed with Egypt getting the better of Mali this time in a match with the lone goal coming early in the second half from Mohamed Hamdy.