Inflation in the 12 months to mid-September hit 7.96%, well below the 8.14% forecast by economists, likely backing the central bank's recent decision of pausing its aggressive rate hiking cycle.
Adding to energy state tax cuts announced earlier this year, oil giant Petroleo Brasileiro SA reduced refinery gate gasoline prices twice since mid-August, leading to lower prices at the pump.
The inflation drop in September, however, was not widespread as prices fell in only three of the nine groups of products and services surveyed, IBGE said - communication, food and beverages, and transportation.
The latest inflation data comes as Brazil's central bank last week chose to keep interest rates unchanged at 13.75%, pausing an aggressive tightening after 12 consecutive increases aimed at curbing high inflation.
William Jackson, chief emerging markets economist at Capital Economics, said the inflation figures confirmed that the monetary tightening cycle was over.