Singapore Changi Airport handled 1.8 percent less cargo in June compared to the same period a year ago.
Some 150,500 tonnes of airfreight were processed at the airport last month compared to 153,300 tonnes year-over-year.
For the first half of the year, cargo volume dipped 2.3 percent to 877,700 tonnes against the same period in 2012.
In contrast, Hong Kong International Airport (HKIA) reported a growth in cargo numbers for the month, rising 1 percent to 337,000 tonnes year-over-year.
The expansion in throughput was primarily due to a 3 percent growth in exports. Cargo traffic to and from North America outperformed other key regions.
For the first six months of the year, tonnage at HKIA increased 2 percent to 2 million tonnes. On a rolling 12-month basis, airfreight grew 3.2 percent to 4.1 million tonnes.