In Tauranga, sale volumes decreased 9.3 per cent from 269 in August 2017 to 244 in September 2017.
The median house price in the Bay increased 7.9 per cent from $507,500 in September 2016 to $547,500 in September 2017.
In Tauranga City, the median house price decreased -0.6 per cent from $628,500 in September 2016 to $625,000 in September 2017.
The median house price in the Bay increased 2.3 per cent from $535,000 in August 2017 to $547,500 in September 2017.
In Tauranga, median house prices declined 0.4 per cent from $627,500 in August 2017 to $625,000 in September 2017.
REINZ regional director Philip Searle said the Bay of Plenty market remained subdued compared to this time last year with both listings and sales down.
However, prices were holding up in a number of areas within the Bay, he said.
"New stock coming on to the market is slow and the spring increase has yet to kick in. There are 30 per cent fewer cash buyers in the market when compared to the same time last year.
"Interestingly, owner occupiers make up about 60 per cent of buyers (whereas in August this group made up 95 per cent of buyers), with the remaining 40 per cent split equally between first home buyers and investors."
REINZ chief executive Bindi Norwell said the soggy start to spring combined with the "election effect" has had a significant impact on the number of sales across the country.
"This is the lowest number of sales in eight months, and the lowest number of sales in the month of September for six years," he said.
"However, it is not all doom and gloom as there are pockets of the country experiencing increases month-on-month and median prices are increasing in the majority of regions across the country."
