The holders started slowly and invited the Ivorians to the first chance on 16 minutes, but Mohamemed Adamu kept the latter at bay with a smart block following a decent attempt.
The Nigerians remained in the contest and launched a few half-chances afterwards, but struggled to crack down the Ivorians who proved hard to unravel.
Neither side though managed to breakthrough in the first half with no clear cut chances propping up on either end and went into the halftime break level pegging.
Nigeria looked to increase the tempo of the match in the 54th minute with their first change in Sunday Maleye, who came on for Olabiran Muyiwa.
The change appeared telling as the Nigerians went on to hit the crossbar following a powering goal-bound header from Orij Okonkow following a corner on 65 minutes.
Nigeria went down to ten men in the final 20 minutes after Olisa Ndah earned his marching orders for conceding a penalty following a foul in the area. Ivory Coast took advantage of the situation and netted the opener from the resultant 12-yard set-play courtesy of Silas Gnaka.
The Ivorians remained strong towards full-time to get their tournament off the mark, as the Nigerians start the defence of their title on the back foot.
