The Cardiff goalkeeper - confirmed in the latest Scotland squad earlier on Tuesday - made a string of brilliant second-half saves as his side ground out a 1-1 draw at the Amex.
Gianni Bruno's 21st-minute volley was cancelled out almost immediately by Kenwyne Jones' header.
Home boss Sami Hyypia praised his side's best performance so far this season, but the Seagulls will be kicking themselves for not taking full points.
They ended their 320-minute goal drought in style when right-back Bruno guided a first-time volley over Marshall from wide on the right and inside the far post.
But Albion surrendered their hard-earned advantage in sloppy fashion.
Goalkeeper David Stockdale rushed out to the edge of his area to meet Fabio's long ball and was beaten to it by Jones, whose brave header bounced into the net.
Stockdale partly redeemed himself after the break with a great block from Anthony Pilkington after an error by Lewis Dunk.
But opposite number Marshall stole the show.
He was quick off his line to smother a Jake Forster-Caskey's superb through ball which looked like setting Craig Mackail-Smith away and had to be alert when a Kazenga LuaLua shot from the edge of the box took a deflection.
Marshall pulled off a superb save to deny Joe Bennett who threw himself at a pinpoint Joao Teixeira cross to send in a diving header and was at his best again to keep out Dunk from a corner.
A ferocious strike from Gary Gardner brought another decent save from the keeper low to his right and Bennett was denied again as the Seagulls piled on the pressure.
His inspired night continued as he palmed away another Gardner piledriver, while the home side felt they were denied a penalty when LuaLua went down in the box but referee Neil Swarbrick waved away the protests and Cardiff held on.