Self-proclaimed Seattle superhero Phoenix Jones, a vigilante crime-fighter accused of assault, made his first court appearance on Thursday, but prosecutors have so far declined to charge him.

The one-time mixed-martial-arts competitor whose real name is Benjamin Fodor was arrested on Sunday after police said he pepper-sprayed a group of innocent nightclub patrons he believed were involved in a street brawl downtown.

He was jailed briefly on suspicion of four misdemeanour counts of assault and released on $US3800 bail.

He showed up for a brief hearing on Thursday in Seattle Municipal Court wearing a pinstriped shirt and his black-and-yellow mask, which he removed at the request of a court officer. He donned it again as he left the courtroom.