TikTok fined 750,000 euros for Dutch privacy violation
"This is an infringement of privacy legislation, which is based on the principle that people must always be given a clear idea of what is being done with their personal data," it added.
The data protection watchdog said it launched its investigation last year into the popular social media service, which has 3.5 million users in the Netherlands.
The EU in May said TikTok must address concerns of aggressive advertising methods targeting children in a case launched by consumer authorities in several member states.
TikTok has faced many such cases globally, and the EU claim came a month after Britain accused the video-sharing app of illegally collecting personal data from millions of children in Europe.
The case by the EU executive came after a signal in February by the European Consumer Organisation (BEUC) about TikTok's alleged breaches of EU consumer rights.