Remittances to Mexico fell 20.24 percent in September compared with the same month in 2011, the largest year-to-year decline in 35 months, the central bank said Thursday.
The September 2012 total was also 13.4 percent lower than the figure for August.
Mexicans working abroad sent home $1.66 billion in September, down from $2.08 billion 12 months earlier.
The number of transactions, 5.6 million, was off 6.1 percent from September 2011 and the median amount per transaction fell from $348.42 to $296.18, the Banco de Mexico said.
Remittances from expatriates are Mexico's second-largest source of foreign exchange after oil exports and help cover living expenses for millions of households.
Most of the money is sent from the United States, where an estimated 12 million Mexicans live, about half of them undocumented migrants. EFE