Nigeria's Super Eagles were under pressure to get a victory after drawing their opening game against Equatorial Guinea and are now all but certain of reaching the knockout stage.
Also, coach José Peseiro’s team finally showed defensive stability as it ended a six-game run of conceding at least a goal.
But it was another frustrating performance from star player Victor Osimhen, despite earning the penalty that facilitated the win.
Referee Mustapha Ghorbal awarded the spot kick after consulting video replays and deciding Ousmane Diomande had fouled Osimhen.
Troost-Ekong took responsibility and confidently fired the penalty down the center of goal in the 55th.
Osimhen missed the game’s best early chance when he shot high and wide after being played through by Samuel Chukwueze.
Nigeria's forward #9 Victor Osimhen (R) fights for the ball with Ivory Coast's defender #3 Ghislain Konan (L) during the Africa Cup of Nations group A football match against Ivory Coast at the Alassane Ouattara Olympic Stadium in Ebimpe, Abidjan, on January 18, 2024.
The home team had more of the ball, but Nigeria edged the number of efforts at goal in the first half — seven compared to six from Ivory Coast.
Seko Fofana drew a good save from Nigeria keeper Stanley Nwabali with a fierce strike from distance around the half-hour mark and went close again in the second half.
The 60,000-capacity Alassane Ouattara Stadium was mostly full for the match, as organizers said all tickets were sold out. The opening games have been affected by ticketing problems. Fans were warned to “stay away from the sun” amid temperatures above 30 degrees C (86 F) and humidity of 75%.
Abidjan was bustling with excited fans long before the game, many wearing its distinctive orange jersey, blowing their horns, and waving the country’s orange, white and green flags.
But Ivory Coast dropped to third in Group A on three points, one behind Equatorial Guinea and Nigeria. Only the top two in each group are assured of progress.
Ivory Coast next faces Equatorial Guinea on Monday, when Nigeria plays Guinea-Bissau for its final group game.
Nsue sets hat trick record
Emilio Nsue scored a hat trick and Equatorial Guinea took a giant step toward the knockout stage with a 4-2 win over Guinea-Bissau in the early kickoff.
Equatorial Guinea's forward #10 Emilio Nsue kicks the ball during the Africa Cup of Nations group A football match against Guinea-Bissau at the Alassane Ouattara Olympic Stadium in Ebimpe, Abidjan, January 18, 2024.
The 34-year-old Nsue became the oldest player to score a hat trick at the tournament, which is in its 34th edition, and the first in 16 years. Morocco's Soufiane Alloudi last managed the feat for Morocco in January 2008.
Nsue capitalized on a defensive mistake to put the “National Thunder” ahead in the 21st minute, only for an own goal from Esteban Orozco to draw Guinea-Bissau level again in the 37th.
Orozco was trying to cut out a cross for Franculino Djú — who was offside — when he turned the ball into his own net.
But José Miranda struck from outside the box after the break and Nsue grabbed his second to effectively seal the result five minutes later. He completed his hat trick by scoring from a difficult angle in the 61st, though he had to endure a VAR review before celebrating.
Substitute Zé Turbo scored Guinea Bissau's consolation goal in injury time but couldn't prevent the country's winless run at the Africa Cup from stretching to 11 games. The “Djurtus” are bottom of the group after losing both games so far.
Ghana and Egypt were playing at Abidjan’s Félix Houphouët-Boigny Stadium later, with the pressure on both teams after failing to win their opening games.