Millwall U18s 3 Brentford U18s 0
The young Bees were looking to halt a recent run of losses in the league.
Eldon O'Boyle opened the scoring as he was quickest to react to a driven cross in the box.
After a slow start, the boys picked up the tempo and Ollie Shield fired an effort that was saved well by the goalkeeper.
O'Boyle finished past Evan Anderson to score his second of the game as the home side were taking control of the game.
A third was scored soon after and it was identical to the second, as William Wright was there to finish from close range after a cross into the box.
Adam Poliakov had a massive chance to reduce the deficit with a one-on-one chance early in the second period, but their keeper stood tall and held his ground to save well.
Second-half substitute Isaiah Powis had the next opportunity, receiving a Poliakov cross, but his shot only just went wide.
Despite some decent chances in the second period, the damage has been done by the first-half goals as the Under-18s suffered a loss.
The young Bees will next be in action on Saturday 2 November as they are away to Cardiff City.
Brentford U18s: Anderson, Trimboli, Asemokhai (Golding, 70'), Klimas, Ivanov, Honor, Poliakov (Francis, 79'), Shield, Ouattara (Powis, 46'), Giscombe, McSorley (Djoro, 61')
Booked: Asemokhai 56
Millwall U18s: Przewozny, Archer, Ashburn, Mansor (c), Taylor, Parkes, Kendall, Whitby, O'Boyle, Wright, Beaumont
Booked: Parkes 20