In doing so, he violated a fundamental principle of judicial ethics and, particularly in view of the controversy surrounding Trumps campaign, engaged in serious misconduct, the council panel wrote.
Mr Zabel has called wearing the hat an "ill-considered" attempt at a joke. The council said the hat incident was an "inexplicable act of judicial misconduct" from an otherwise respected judge.
The decision came after the Ontario Judicial Council panel met last month for a one-day hearing into the complaints against Zabel for wearing the red "MAGA" hat on November 9, 2016, one day after Trump won the presidency.
The council received 81 complaints about Justice Zabel, including one signed by 27 faculty members of the law school at the University of Windsor in Ontario, which the justice had attended.
Suspension without pay is the most serious sanction the Ontario Judicial Council can impose other than complete removal from office. The Ontario Court of Justice said in January that Zabel, who is based in Hamilton, was no longer being assigned cases.
"Whatever Justice Zabel may have thought about the USA presidential election, and however serious his actions ... his record on the bench and his reputation with his judicial colleagues and the bar demonstrates that he is an entirely fair-minded and impartial judge who is dedicated to the highest ideals of his calling", the panel said.
"Justice Zabel is anxious to return to work", Giulia Gambacorta said in an e-mail to The Globe and Mail.
But when it ended, the court papers said, he said to a prosecutor that the hat's "brief appearance" was meant to annoy the rest of the judges because he thought they were Clinton supporters.
He testified that it was only after his actions made headlines that he realized some believed he was showing support for the controversial American president and his policies.
Zabel wore the hat while walking into a courtroom and said it was "just in celebration of a historic night in the United States", according to an agreed statement of facts. He said he had bought several MAGA hats as historical memorabilia, not as a Trump supporter. Zabel later apologized publicly for his behavior, calling it a "lapse in judgment".