TiKTok chief executive Shou Zi Chew held talks for the first time with EU vice-presidents Margrethe Vestager and Vera Jourova, the bloc's home affairs commissioner Ylva Johansson and justice commissioner Didier Reynders.
TikTok, whose parent company ByteDance is Chinese, has come under fierce Western scrutiny in recent months amid concerns over how much access Beijing has to user data.
I count on TikTok to fully execute its commitments to go the extra mile in respecting EU law and regaining trust of European regulators," Jourova, whose portfolio includes the protection of EU values, tweeted alongside a video of their meeting.
"There cannot be any doubt that data of users in Europe are safe and not exposed to illegal access from third-country authorities," she added.
In November, TikTok admitted some staff in China can access the data of European users -- but Chew told Jourova the company was working on a "robust" system for processing Europeans' data in Europe, an EU spokesman said.
ByteDance is already under investigation by the Irish privacy regulator, the DPC, over whether it violated the EU's data protection law, the GDPR, in the way it processed children's personal data and over transfers of data to China.
"I insisted on the importance for TikTok to ensure full compliance with GDPR and cooperate with the DPC," Reynders said.
The EU has also stepped up its fight against disinformation with a strengthened code of practice and Jourova said TikTok would deliver a first report on the issue by the end of January. "Transparency will be a key element."
The EU has built a powerful legislative arsenal targeting technology companies, passing two major laws to ensure social media platforms follow the bloc's rules on digital issues.
The Digital Services Act (DSA) forces social media platforms, online marketplaces and search engines to react more quickly to remove content deemed in breach of EU regulations.
The other, the Digital Markets Act (DMA), prohibits anti-competitive behaviour by the so-called "gatekeepers" of the internet.
Jourova warned TikTok and others must "swiftly get ready for compliance with the new EU digital rulebook", referring to the DSA and DMA.
Last month, TikTok admitted ByteDance staff accessed data from the app to track journalists in a bid to identify the source of leaks to the media.
The company strenuously denies Beijing has any control or access.
But Washington has banned the app from federal government devices while some US lawmakers are trying to prohibit TikTok operating in the United States.
Last year TikTok said it was working on a plan to allay Washington's concerns by holding US users' data in the United States.