The ANZ World Commodity Price Index dipped 2.8 per cent in May, driven down by weakness in aluminium, dairy and forestry.
But, in local currency terms, the index gained 2 per cent, due to the NZ dollar depreciating sharply on a trade-weighted index (TWI) basis.
It was the second monthly fall in a row with the index dropping 1.9 per cent in April and 0.8 per cent on a currency-adjusted basis.
The index peaked at a record high in March.
On an annual basis the index of New Zealand's major export commodities is still up 7.8 per cent on last May - or 18.5 per cent in New Zealand dollar terms.
The kiwi dollar was trading at US70c in March but has slipped back as the US Federal Reserve has lifted interest rates.
It slid as low as US63c in May but has rebounded and was trading at US65c today.
The ANZ index showed dairy prices fell 4.8 per cent month-on-month in May, reflecting falls in the latest Global Dairy Trade auction.
The meat and fibre index gained 0.5 per cent in May as higher prices for lamb and wool offset a decrease in the price of beef.
Meat processing capacity has been curtailed this season due to a shortage of labour.
The smaller volumes of lamb processed so far have helped export prices to recover.
Beef prices have been impacted by recent logistical challenges getting product into China, which has meant more meat being diverted to the United States, which tends to be a lower-value market.
The horticulture index lifted 1.9 per cent in May in world price terms. Higher apple prices were recorded in European markets.
International demand for kiwifruit remained strong.
Aluminium prices dropped 12.4 per cent, continuing the downward trend from the previous month.
In a promising sign for those watching global inflation trends shipping prices were starting to ease.
"Global shipping prices have generally eased over the past month as the export of goods out of China has slowed," said ANZ Agri Economist Susan Kilsby.
"But prices paid by our local exporters to freight produce internationally remain firm."
"Refrigerated shipping containers are in tight supply, and getting shipping space remains a challenge," she said.
"Limited cool-storage capacity within New Zealand is putting pressure on exporters to move product, which means some goods have been diverted to other markets due to the congestion at Chinese ports."