Two court-appointed psychiatrists found that the Princeton grad charged with fatally shooting his millionaire hedge-fund dad was too mentally ill to proceed to trial, a judge said Thursday in Manhattan court.

Thomas Gilbert Jr., 30, has been in custody since his arrest for allegedly blasting his father, Thomas Gilbert Sr., point-blank in the head Jan. 4.

“The defendant has been found unfit,” said Justice Melissa Jackson as Gilbert Jr.’s mom, Shelley, and sister Clare watched from the gallery.

Gilbert Jr. sat at the defense table in an orange jumpsuit with his hands cuffed behind his back.

Assistant District Attorney Craig Ortner asked the judge for another week to decide whether the Manhattan District Attorney’s Office would challenge the findings.

The psychiatrists recommend that Gilbert Jr. be transferred to a state hospital for treatment until his mental condition stabilizes.

Defense lawyer Alex Spiro requested the mental health exam at Gilbert Jr.’s last court appearance in July shortly after media reports surfaced about the troubled son’s increasingly erratic and irrational behavior in jail.

Spiro previously notified the court that he planned to put on a psychiatric defense.

Prosecutors claim that the trust-fund layabout murdered his father, the founder of hedge fund Wainscott Capital, after the father had slashed the son’s $200 stipend.

His mother discovered her slain husband on the floor of their Beekman Place pad with a .40-caliber Glock resting on his chest.

Gilbert Jr. allegedly tried to stage the scene to look like a suicide, prosecutors said.

He faces 25 years to life if convicted at trial.

“I hope Mr. Gilbert will get the treatment that he needs,” said Spiro.