Statistics Canada says the national inflation rate in May was down by 0.4 per cent on a year-over-year basis.
That is down from a year-over-year decline of 0.2 per cent recorded by the agency in April.
Transportation prices contributed the most to the decline in the consumer price index, mainly because of lower gas prices.
StatCan says excluding gasoline, the consumer price index rose by 0.7 per cent, the smallest increase since January of 2013.