The average cost of a property fell by 0.2 per cent to £164,210 – the first drop since August 2013.
Prices fell in more than half of local authority areas across the country, including Edinburgh, Aberdeenshire, South Lanarkshire, East Dunbartonshire and Fife.
However, prices were up 5.7 per cent on the same period last year, according to the LSL Property Services/Acadata Scotland House Price Index for August 2014.
The prospect of the Scottish independence referendum in September hindered activity in the housing market, the report found.
Sales in August were 8 per cent down on July 2014, although 7 per cent higher than August 2013.
Gordon Fowlis, regional managing director of Your Move, said: “The powerful spell of growth cast over the Scottish property market was broken in August, as house prices fell for the first time in a year.
“At a time when property values across the rest of the UK were continuing to grow, Scotland moved against the grain and average house prices dropped across more than half the country.
“It’s been an unpredictable and momentous few months in Scotland’s history. In August, uncertainty was still rife over the outcome of the independence referendum, and this hindered the pace of activity in the housing market.
“Sales in August were 8 per cent below the typical seasonal trend, as sellers shirked the market and buyers postponed purchase decisions until the dust settled. This trend appears more acute at the top tiers of the market, where there were bigger investments at stake, and there was an 11 per cent drop in the number of homes sold across Scotland for over £1 million between July and August.”
Fifteen properties sold for more than £1m in August, including nine in Edinburgh, two in Glasgow and one in Aberdeen. Orkney saw the biggest monthly rise in prices in August, with a 6.5 per cent increase, while on the mainland East Renfrewshire led the field with a 4.4 per cent boost.
On an annual basis, prices have risen in 27 of the 32 local authority areas, which is three fewer than last month.