After two days on the social-media app, the US president has 11,000 followers.
TikTok was banned in India two months ago. Mr Trump wants to follow suit unless it sells the app's US version and has signed executive orders targeting both it and another Chinese social-media app, Tencent's WeChat.
Both India and the US fear data collected by the TikTok could be given to the Chinese government.
TikTok strongly denies this and says none of its international users' data is stored in China.