August's figure was 24.3 billion patacas ($3.01 billion), Macau's Gaming Inspection and Coordination said in data posted on Sunday, below analysts' expectations of a drop of 2%-6%.
The figure was slightly lower than July's monthly revenue of 24.4 billion patacas.
While protests in the Asian financial hub of Hong Kong have disrupted transport and deterred travel to the former British colony and then on to Macau, analysts say the impact on gaming revenues has been minimal.
However, the protests have added to the impact of factors such as a typhoon earlier in the month that hit China's coastal cities and tightening liquidity in the high-roller VIP sector.
Macau's biggest junket operator, Suncity, which operates VIP gambling rooms around Asia, was singled out by state media in July as raking in billions of dollars in online gaming and proxy betting, "causing great harm to China’s social economic order".
"The negativity surrounding Suncity continues to pressure junket VIP, as some agents withdraw some funds and some VIP players delay visiting Macau," said Vitaly Umansky, an analyst at Sanford C. Bernstein in Hong Kong.
(Reporting by Farah Master; Editing by Clarence Fernandez)