Yaya Toure gave Ivory Coast a mid-first half lead, Dieumerci Mbokani equalised from a penalty, Gervinho restored the lead before half-time and Serge Wilfried Kanon added a third goal.
Renard guided outsiders Zambia to glory in 2012 with a penalty shootout final victory over Ivory Coast.
The Frenchman hopes to become only the third coach after Ghanaian Charles Gyamfi and Egyptian Hassan Shehata to win the Cup of Nations more than once.
In the final on Sunday, Ivory Coast will face hosts Equatorial Guinea or favoured Ghana, who clash Thursday in Malabo.
There were few secrets between the teams going into the match at far-from-full Estadio de Bata as they met twice in the qualifying competition.
Ivory Coast triumphed 2-1 in the Democratic Republic of Congo last October only to suffer a shock 4-3 home loss four days later.
DR Congo coach Florent Ibenge made one change from the team that started in a come-from-behind 4-2 quarter-final win over Congo Brazzaville with defender Joel Kimwaki replacing Cedric Mongongu.
Renard kept faith with the team that began in a 3-1 last-eight victory over top-ranked African team Algeria.
The Ivorian Elephants are ranked 10 places above the Congolese Leopards in Africa, but it was the central Africans who began brightly.
Mbokani had the first chance on six minutes, but fired over after a Sylvain Gbohouo parry from a snap Jeremy Bokila shot fell into his path.
Serey Die blazed wide at the other end on 15 minutes after he picked up the headed clearance of a Yaya Toure free-kick.
Ivory Coast took the lead five minutes later with a memorable first goal of the tournament from reigning African Footballer of the Year Yaya Toure.
Wilfried Bony lost possession inside the box and the ball ran loose to Yaya Toure, who belted the ball over 39-year-old goalkeeper Robert Kidiaba and into the net.
A needless hand-ball from Eric Bailly presented DR Congo with a penalty and Mbokani calmly placed the ball into the corner of the net for a 24th-minute leveller.
The Ivorians were fortunate seven minutes from half-time when burly Mbokani connected poorly with a cut-back and the ball was deflected for a corner.
It was then the turn of Ivory Coast to apply pressure and Gervinho saw a header rebound off the crossbar before he scored on 41 minutes.
The dreadlocked winger, unmarked in plenty of space, latched onto a Bony pass and side-footed the ball into the net off a hand of Kidiaba.
Ivory Coast looked more likely to score as the second half progressed and a third goal came on 68 minutes.
Kidiaba did well to block a Serge Aurier header off a corner only for Kanon to score off the rebound with the ball entering the net via his knee.