A penalty from Olusegun Olakunle in the 21st minute was all that was needed for the Golden Eaglets of Nigeria to book a place in the semi-final of the U17 African Cup of Nations.
The spot in the semi-final also means Nigeria has qualified for the 2019 FIFA U17 World Cup scheduled to hold in Brazil.
Golden Eaglets' coach Manu Garba made one change to the lineup that started the Tanzania game. Goalkeeper Suleiman Shaibu who conceded four goals was replaced with Sunday Stephen.
Stephen proved his mettle between the sticks with a string of saves during the game. In the 11th minute, the goalkeeper was on hand to stop a goal-bound lob.
Wisdom Ubani, who scored a free-kick against Tanzania, almost hit the target with his freekick in the opening stages.
The lone goal of the game came after an Angolan defender handled the ball in the area, the referee spotted the handball and awarded a penalty that was smartly converted by Olakunle.
The youngsters were profligate in front of goal spurning chances that could have made the lead more comfortable.
In the 42nd minute, Shedrack Tanko was clear on goal but he couldn't hit the target with his effort hitting the upright. Two minutes later, Olusegun opted for a cheeky lob when presented with a chance but Geovani, Angola's goalkeeper stopped the effort.
Nigeria finished the first half with five of their seven shots on target.
Angola was reduced to ten men when the referee showed Gege a second yellow in the 51st minute.
Garba brought on Ibraheem Jabaar for Olatomi Olaniyan in the 60th minute but the Golden Eaglets couldn't take advantage of Angola's red card.
The game finished with a clean sheet for Sunday and the much-improved defence while the attackers missed a number of gilt-edged chances.
Nigeria will play Uganda on Saturday by 2:00pm to complete the group stages.
Nigeria's opening game in the tournament was a dramatic 5-4 win over hosts Tanzania.
The Golden Eaglets will make their 12th appearance at the FIFA U17 World Cup set to hold in Brazil.