The benchmark IPCA index of inflation rose 2.89pc in the 12 months through September, down from an increase of 3.43pc in the previous month, government statistics agency IBGE said on Wednesday.
This was below the median consensus forecast of 2.97pc in a Reuters poll of economists and marked the first time since May last year that the annual rate of inflation has been below 3.0pc.
The central bank's official year-end goal for 2019, remains 4.25pc, a target most economists think will be undershot.
In the first nine months of the year, the annual rate of inflation was running at 2.49pc, IBGE said.
On a monthly basis, prices fell in September for the first time this year, slipping 0.04pc. This is only the fourth month of consumer price deflation in the last five years, IBGE figures show.
The biggest weight in September's data was a 0.43pc month-on-month fall in food and drink prices, IBGE said, followed by a 0.76pc decline in the cost of household goods. Communications was the only other category that saw a fall in prices, albeit a slender 0.01pc.
Of the remaining six categories, the biggest driver was a 0.58pc increase in the cost of health and personal care items, IBGE said.
Citing low inflation, Brazil's central bank reduced benchmark borrowing costs last month to a new low of 5.50pc. Economists widely expect it to cut again later this year.