The tech giant was hit hard by a government clampdown on game approvals and playing time.
Chinese regulators have not yet given the firm a new gaming license after they temporarily stopped approvals.
Tencent said revenue fell 3% to just under $20 billion for the three months ended June.
Net profit fell by more than half to around $2.7 billion - below analyst forecasts.
The company also dealt with a weakening economy that has led to advertisers spending less than before.
Ad revenue fell by almost a fifth as a result.
Online gaming is Tencent's big profit driver, but that was down both at home and abroad.
The quarterly loss is new territory for the Chinese firm, as it had reported double digit growth in almost every quarter since it went public in 2004.
It's not just Tencent feeling the pain in China's tech sector.
E-commerce giant Alibaba reported flat quarterly revenue growth for the first time in its history this month.
Reports also said Tuesday (August 16) that Tencent planned to sell most of its $24 billion stake in delivery firm Meituan.
Sources said that was partly to please Chinese regulators.
Tencent has lost almost 60% of its market value since it peaked in February last year, but the $373 billion company is still China's most valuable.