Djibril Gueye, Assane Mbodji and Abdoulaye Ba scored to ensure the Teranga Lions’ progression to the quarter-finals, while Claudio Gomes pulled a goal back for Guinea Bissau.
Victory for Senegal was always coming with Gueye opening the scoring 10 minutes into the match when he pounced on a loose ball after his initial shot had been cleared.
The Teranga Lions doubled their advantage through Mbodji when he was set up by Elhadji Moutarou Balde on the half-hour mark.
This sparked a response from Guinea-Bissau who reduced arrears through first-half substitute Gomes who made no mistake after beating two Senegal defenders before slotting home from close range five minutes before the breather.
But the hosts could have gone to the half time break enjoying a comfortable lead had Balde not narrowly missed the target and also had the post not denied striker Youssouph Mamadou Badji’s effort.
Guinea-Bissau almost equalised 14 minutes after the restart but Tigana Quebe shot over and failed to make the most of a fumble by the Senegal goalkeeper.
As the Wild Dogs pressed to level matters, Senegal increased their lead through Ba with four minutes remaining to ensure the important victory.
Meanwhile, Burkina Faso beat Mauritania 4-3 on penalties after coming from behind to force a 1-1 regulation time draw at the same venue in a later match.
Following a goalless first half, Taghiyoullah Denne put Mauritania ahead in the 73rd minute, before Yannick Pognongo saved the day for Burkina Faso with an equaliser four minutes from time.
Burkina Faso dominated the first half with Rene Zoungrana being denied by the post while Issouf Zonon also came close but had his long-range shot saved by the Mauritania goalkeeper.
Captain Denne then stunned the Stallions with a deflected freekick for Mauritania's opener.
But in-form Pognongo whose goal sank Ghana in the 2020 African Nations Championship qualifiers a week earlier was again the hero for Burkina Faso on Saturday.
He equalised from the penalty spot after Mohamed Mbar Mohamed had fouled Clement Pitroipa inside the box, to send the contest to a penalty shootout from where Burkina Faso completed a comeback to win the battle.
Burkina Faso goalkeeper Aboubacar Sawadogo was the hero of the shootout, denying Ahmed Rachid as Pognongo returned to slot home the winning penalty for the Stallions.
The result saw Burkina Faso qualifying for the quarter-finals of the tournament where they will meet the winner between Ghana and Gambia while Mauritania will now play in the Plate quarter-finals.