Brest appeared to be the victim of an international break hangover as they made a sluggish start to proceedings in the principality.
The visitors ultimately had no answer to Monaco's fifth-minute counter-attack, with Maghnes Akliouche and Eliesse Ben Seghir combining for the former to fire in at the near post.
Akliouche should have registered a swift second when he found himself one-on-one with Marco Bizot, only to thump his right-foot strike against the post.
Fortunately for Akliouche, that miss did not prove too costly as Brest gifted the hosts the chance to double their advantage in the 24th minute.
Aleksandr Golovin was more than happy to collect a loose Brest pass on the edge of the box, before driving the ball in off the upright to score his first Ligue 1 goal since February.
After being left disappointed with his team’s first-half performance, Brest boss Eric Roy opted to turn to his bench at the break, introducing Kamory Doumbia for Romain Del Castillo.
The Mali international required just five minutes to make an impact, whipping in a near-post corner for the towering Abdallah Sima to head past the helpless Radoslaw Majecki.
While they may have gained a crucial foothold, Brest were given a scare when referee Thomas Leonard pointed to the spot following Bizot’s rash challenge on Christian Mawissa, only for the offside flag to come to the goalkeeper’s aid.
Brest continued their desperate search for an equaliser until their hopes of salvaging a point were extinguished by Akliouche’s exquisite late lob over Bizot.
Ludovic Ajorque netted in the 96th minute to reduce the deficit but it ultimately proved to be a mere consolation as the 12th-placed visitors fell to their third consecutive league defeat, spurning the chance to build confidence ahead of their UEFA Champions League clash with Barcelona.
Meanwhile, victory for Monaco keeps them second in the table, three points behind leaders Paris Saint-Germain with a game extra played.
Flashscore Man of the Match: Maghnes Akliouche (AS Monaco)