The ruling came hours after another judge rejected the top Kremlin critic’s appeal over his prison sentence for violating the terms of his probation.
The court convicted Navalny on charges of slandering a Second World War veteran and ordered him to pay a fine of 850,000 rubles (about £8,200).
Navalny, who called the 94-year-old veteran and other people featured in a pro-Kremlin video last year “corrupt stooges”, “people without conscience” and “traitors”, has rejected the slander charges and described them as part of official efforts to disparage him.
Earlier on Saturday, Navalny lost his appeal over a prison sentence for violating the terms of his probation while recuperating in Germany from a nerve agent poisoning which he blames on the Kremlin.
A Moscow City Court judge reduced the sentence from two years and eight months to just over two and a half years.
The verdict came even as the country faces a top European rights court’s order to free Navalny.