Three self-described “day traders” were convicted of embezzling almost $6 million from Columbia University yesterday.

The defendants in the brazen theft — in which $5.7 million was electronically emptied out of the school’s coffers in fall 2010 — had contended the money simply turned up in their accounts.

Prosecutors said it was well-organized scam masterminded by George Castro, 49, with the help of two employees from the school’s accounts payable department.

Former university clerk Moise Jeanpaul, who testified under a cooperation agreement, told jurors that he conspired with fellow employee Joseph Pineras to alter a routing code to divert the loot into a bank account controlled by Castro.

The money was supposed to the university’s affiliate hospital, New York-Presbyterian.

Castro was busted outside his Bronx home in Dec. 2010 as he was getting inside his brand new, $80,000 Audi Q7 while carrying bags of $100 bills totaling $200,000.

Castro, Pineras, and the remaining defendants, Walter Stephens, Jr. and Jeremy Dieudonne, who acted as his own lawyer, will be sentenced on Sept. 24.