The win cleared doubts surrounding the Black Stars title winning credentials and confirmed their status as one of the firm favourites.
Niger were the first to drop their statement of intent when skipper Moussa Maazou wheeled past the Ghana left-back Harrison Afful to send in a cross which was cleared away by Isaac Vorsah with a sliding effort.
The Black Stars kept their composure and kept pressing high up which yielded in a free-kick after Kwadwo Asamoah felled.
It took just six minutes for Ghana to find the opener through Gyan which happened to be his first of the tournament.
Albert Adomah did all the damage on the right wing before sending a cross which found Gyan inside the box and with a good first touch, he blasted past goalkeeper Dauoda Kassali.
Two minutes later, a long ball from midfield found Maazou but he failed to control inside the Ghana box with his head as the ball went over the touchline.
Referee Diata Badara disallowed a tenth minute goal from Niger as the centre man penalized Maazou for fouling Fatau Dauda who had gone in for a corner-kick but televison replay showed it was a legal challenge.
After a quarter of an hour play, Niger defender Mohammed Chicoto attempted a bicycle kick inside Ghanaâ€™s box which went wide.
The Black Stars went on to earn a free-kick courtesy Asamoahâ€™s widzardry which was too much for Issiakou Koudize but Gyan curled a straight one for Kassali to grab.
On 23 minutes later, debutant Christian Atsu planted the second goal by finishing off an attack he began.
The FC Porto player raced with the ball before getting it to Gyan who drifted to the left and sent in a cross.
Atsu brough it down onto his chest and shrugged off a challenge before cooly stabbing it in for his first goal of the tournament.
Ghana twice went on the counter bfore the half-hour mark but nice interventions by the Niger backline prevented a goal harvest.
Maazou skipped past John Boye but his incisive cross went past the face of Ghanaâ€™s goal with nobody to connect. Striker Sidebe Modibo was late.
Again Maazou teed up Modibo with a back flick header but the latter was slow to react as Vorsah went in with a big-boot clearance.
Badu powerful shot cleared by Kassaly out-stretched left arm after a nice move from Kwadwo Asamoah.
A mix-up between Adomah and Rabiu on the counter denied Ghana the thirdÂ goal for 2-0 lead at half-time.
Four minutes after the break, Asamoah sent in a free-kick which was knocked down by Gyan but Kassali spilled it and Boye connected the rebound for the third goal.
It was Boyeâ€™s first Nations Cup goal in two appearances at the finals.
In the 51st minute, another corner kick was not dealt with by Niger but Kassali was fast to clutch it this time round.
Maazou came in with a powerful header inside the Ghana box which was threatening but it was wide.
The Etoile du Sahel man cut in from the right but his cross swept past the face of Ghanaâ€™s goal and missed everybody including the goalkeeper few minutes later.
On 62 minutes, Atsuâ€™s brilliance saw him slalom past his markers before releasing Gyan who shot feebly into the waiting arms of Kassali.
Another opportunity went to Gyan but he failed to connect Adomahâ€™s prosaic cross from the right.
Niger never gave up and piled pressure but Ghanaâ€™s defence was resolute and never gave anything away.
Ghana go into the last eight hugely motivated against the Blue Sharks on Saturday at the Nelson Mandela Bay Stadium.