Ross County Common Pleas Judge Scott Nusbaum was photographed at a party wearing dark makeup, a pink dress and a gray wig, the Chillicothe Gazette reported.
Local NAACP President Olie Burton, who met with Nusbaum on Friday, said the judge explained that he chose to dress as a servant while Nusbaum's wife dressed as Scarlett O'Hara from "Gone with the Wind."
Nusbaum told the Gazette he regrets the costume and called it thoughtless and insensitive.
"Although it was stupid, I certainly didn't do it maliciously," Nusbaum said. "I was born in this community and I'm sorry I let my community down."
Burton said he considers the costume choice out-of-character for the judge.
"We left with an understanding that we know it was in poor taste, but we accept his apology and this is not in his character," Burton said.
Nusbaum acknowledged the possibilities that the costume could create a perception of bias in his work and could prompt disciplinary action from an Ohio Supreme Court board if it were to be deemed unethical conduct.
The rules for judges call for "promoting confidence in the judiciary" and say that can be eroded by personal or professional conduct "that creates the appearance of impropriety," the newspaper said.
Nusbaum, a former county prosecutor, said he's always been objective in handling cases. He was elected in 2006 and re-elected in 2012, both uncontested races.
The county public defender, Susan Pettit, said she and her staff consider Nusbaum to be a fair judge and don't feel the costume choice is representative of him.
Several other blackface costumes made national headlines this past Halloween and spurred criticism. Actress Julianne Hough apologized after she was criticized for darkening her skin for a costume as the character Crazy Eyes from the show "Orange is the New Black."