No official explanation was offered for the Pooh policy, but observers cited previous viral posts that compared the country's president to the portly bear.
An image comparing Pooh and fellow stuffed animal Tiger to a photo of President Xi Jinping and then-U.S. President Barack Obama went viral in 2013, and political consultancy firm Global Risk Insights said another meme comparing Pooh and Xi was China's most censored image of 2015.
Social media users reported attempts to use the Chinese-character version of Winnie-the-Pooh's name on Weibo resulted in a "content is illegal" message popping up. Some users seemed able to get around the ban through unknown means.
The social media ban comes amid an escalation in online censorship ahead of the Communist Party Congress, an event in the fall where key political appointments will be announced.
"Historically, two things have been not allowed: political organizing and political action. But this year a third has been added to the list: talking about the president," Qiao Mu, assistant professor of media at Beijing Foreign Studies University, told the Financial Times of the Communist Party Congress.
Qiao said said some Internet users have been detained by authorities after posting comments about Xi.
"I think the Winnie issue is part of this trend," he said.