Posting a photo of himself and Foreign Minister Heiko Maas on his Twitter account, the 22-year-old said they spoke on the "protest situation and our cause to free election and democracy in HK."
Beijing reacted angrily at their meeting during an event organized by Bild daily, saying "it is extremely wrong for German media and politicians to attempt to tap into the anti-China separatist wave."
"It is disrespectful of China's sovereignty and an interference in China's internal affairs," said Chinese foreign ministry spokeswoman Hua Chunying.
"I want to stress once again that Hong Kong affairs are purely China's internal affairs. No foreign government, organization or individual has the right to intervene," Hua said, adding that Beijing "strongly disapproves" of the meeting.
Wong, a prominent face in Hong Kong's growing pro-democracy protests, planned to hold talks with other German politicians during his visit to Berlin.
But there are no plans for Chancellor Angela Merkel to meet him, said her spokesman Steffen Seibert on Monday, September 9.
The activist's visit came on the heels of Merkel's trip to China, where she stressed Friday, September 6, that the rights and freedoms of people in Hong Kong "must be guaranteed," after meeting Chinese Premier Li Keqiang in Beijing.
Ahead of her three-day visit to China, demonstrators in the semi-autonomous city appealed to the German chancellor to support them in her meetings with China's leadership.
Wong himself had written an open letter to Merkel, seeking her backing.
'Hong Kong the new Berlin'
Germany has emerged as a country of refuge for a number of Chinese dissidents in recent years, including Liu Xia, the widow of Chinese Nobel dissident Liu Xiaobo.
In May, two former Hong Kong independence activists were granted refugee status in Germany in what is one of the first cases of dissenters from the enclave receiving such protection.
Wong had arrived in Berlin late Monday after he was briefly detained in Hong Kong just before his departure to Germany following an error in his bail conditions from a previous detention.
He was among several prominent democracy advocates held late last month in a roundup by police as the city reels from more than 3 months of unprecedented pro-democracy protests.
Bild reported that Wong turned up late at the event it organized, but was still able to meet Maas at the gathering.
In a brief speech at the event, Wong vowed to "protest until the day that we have free elections."
"If we are now in a new Cold War, Hong Kong is the new Berlin," he said, referring to the post-war split between communist East Berlin and the democratic West.
"'Stand with Hong Kong' is much more than just a mere slogan, we urge the free world to stand together with us in resisting the autocratic Chinese regime," he added.
Wong was due to hold a public discussion on Wednesday evening, September 11, at Humboldt University in Berlin and later travel to the United States.
He launched his career as an activist at just 12 years old and became the poster child of the huge pro-democracy "Umbrella Movement" protests of 2014 that failed to win any concessions from Beijing.
Wong has previously been jailed for involvement in those protests. – Rappler.com