The Canadian Real Estate Association is cutting its forecast for Canadian home sales this year and next.
The industry group is also lowering its national average price forecast.
The group says the change follows a tightening of mortgage lending regulations by the federal government.
Sales in August slipped 5.8 per cent compared with July and were down 8.9 per cent compared with August a year ago.
The month-over-month change was the largest decline since June 2010.
Sales of previously owned Canadian houses and condos have now gone down in five of the past six months.