The youngster fired home 12 minutes from time to give the side a deserved win on the road.
Brentford B Head Coach Neil MacFarlane had a strong side to choose from with first teamers Ellery Balcombe, Shandon Baptiste, Halil Dervisoglu and Marcus Forss all starting against Palace. The home side also made a strong selection with Luka Milivojević and James McCarthy starting amongst a talented XI.
It was the young Bees who started the better of the sides and will have been slightly frustrated not to have gone in at the break a goal to the good having created some good openings early on.
Arthur Read would have an early effort from distance come off the top of the crossbar, whilst Dervisoglu worked it well on the edge of the box with Forss but his powerful drive was well blocked.
The home side's first real opening came when Milivojevic curled a free-kick into the box which was initially headed clear by Kane O'Connor, but in the next phase of play, Brandon Pierrick shot low but Balcombe collected.
Fin Stevens, who threatened frequently down the right-hand side, continued to pose a real threat, and it almost paid off when he cut the ball back for Dervisoglu, whose guided finished was just wide of the far post.
A Paris Maghoma free-kick which edged just over would precede another good Brentford chance when Stevens fired in a low cross for Forss to flick towards goal and saved well, meaning it would be goalless at the break.
The first chance after the break feel to Max Meyer who was found by a Pierrick cross from the left and his guided header was straight at Balcombe who collected comfortably.
Brentford's first chance of the second period fell to Marcus Forss when he latched onto a Baptiste through ball before darting in from the left and forcing the Palace keeper into a smart stop.
A chance would fall to Pressley, but for the offside flag, and the striker had a good chance to make it 1-0 on 72 minutes when The Bees pinched possession high up field but he was unable to keep his low effort on target.
The Brentford forward kept his head up, however, and managed to grab the all-important goal when a corner drifted to the far post before he controlled and slammed home to make it 1-0.
Both sides made a number of changes going into the latter stages of the game and chances became fewer. With Neil MacFarlane's side content with their lead they did well to frustrate their opponents who created very little.
Brentford B: Balcombe, Koutsimouka, Gordon (Trialist, 80), Read (Trialist, 56), O'Connor (Crama, 56), Baptiste, Dervisoglu (Trialist, 70), Maghoma (Carre, 80), Pressley (Hercules, 80), Forss (Trialist, 70), Stevens (Trialist, 85)
Crystal Palace: Henderson, Kelly, Jach, Woods, Inniss, Meyer, Milivojevic, McCarthy, Pierrick, Kirby, Kymani-Gordon
Subs: Goldman, Adaramola, Thiselton, Wells-Morrison, Gonzalez, Mooney, Omilabu, Akinwale, M Boateng.