Jurors found Catherine Kieu guilty of torture and aggravated mayhem for the July 11, 2011, attack.
Sentencing was scheduled for June 28. Kieu faces a maximum sentence of life in prison with possibility of parole, the Orange County district attorney's office said.
"This woman went to extreme lengths to destroy this man's manhood by placing it in the garbage disposal," Deputy District Attorney John Christl said in an interview after the verdict. "She did this out of vengeance, vanity and jealousy."
During trial, the 60-year-old victim testified that his penis could not be reattached and that he felt as though he had been murdered.
Christl told jurors that Kieu, 50, drugged the man's tofu with sleeping pills and screamed "You deserve it!" before attacking him with a 10-inch kitchen knife.
Kieu was jealous and angry about her husband's plans to divorce her because he was seeing his ex-girlfriend, the prosecution said.
Audio of the incident was captured by a voice-activated recorder Kieu had hidden in the bedroom, Christl said.
The man, who is not being named by The Associated Press because of the nature of the attack, married Kieu after they met at a gym but soon subjected Kieu to verbal and sexual abuse, Kieu's public defender, Frank Bittar, said during trial.
Kieu had mental health problems caused by a childhood full of molestation and other trauma in war-torn Vietnam, and her husband also constantly demanded sex in ways that caused her pain, Bittar said.
Bittar did not immediately return a call seeking comment after the verdict.
The prosecutor discounted that argument.
"I think the jury was able to see through the evidence," Christl said after the verdict. "There were no facts or evidence presented other than the defendant's own statements to her doctor about sexual abuse."