The latest figures do, however, represent a 294% increase in revenue from the record-lows of Q2 2020.
Such lows were caused by mandatory casino closures across the country due to the ongoing COVID-19 pandemic.
But operations have since improven dramatically thanks to the reopening of casinos in recent months, with strict health and safety measures in place throughout each venue.
Social distancing measures and capacity restrictions have been key to the industry’s recovery.
A total of 911 US casinos have partially reopened across 40 states, including 442 commercial casinos and 469 tribal properties.
Slot revenue was responsible for $5.87bn of the $9.04bn total, a 19.3% year-on-year decrease.
Table game revenue also declined by 31.2% to $1.57bn.
But both sports gaming and online gaming witnessed revenue rises, with the former increasing 47.1% to $352.3m, and the latter increasing 232.4% to $435m.
“Our industry continues to prioritize the health and safety of our employees, customers, and communities above all else,” said AGA president and CEO Bill Miller.
“While these quarterly results are promising, the reality is a full recovery is dependent on continued public health measures to control prevalence rates.
“As state and local officials respond to current COVID-19 outbreaks with additional restrictions, urgent Congressional action to provide COVID-19 relief is even more crucial. Gaming employees and communities depend on it.”