Police said a teenager was arrested after two men were allegedly stabbed at the centre in the north of the city.
The pair were rushed to hospital and one man in his 20s later died. The other is said to be in a stable condition with a minor injury.
It is not clear whether the two victims were members of the Church of Scientology, and whether the attack happened in the centre or outside.
The 16-year-old "was taken to Chatswood Police Station where he is assisting with inquiries" said New South Wales police.
The centre was opened in 2016 by David Miscavige, the leader of the Church of Scientology, and serves as the headquarters for the organisation in Australia.
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