Family farm income fell by 15% last year to an average of €25,483.
The figure was contained in the Teagasc annual report, which also reveals how the wet weather in the summer of 2012 impacted production costs and crop yields for farmers.
Teagasc is the country's food and agriculture development authority.
The organisation says the inclement weather was particularly challenging for livestock farmers.
Almost a third of those surveyed reported being short of silage.
Many farmers said they'd also depleted their stock of winter fodder by early autumn. Teagasc says direct costs for dairy farms increased by 21%.
The authority says farmers continue to be highly reliant on direct support payments. The average payment per farm stands at just over twenty thousand euro, and makes up 81% of farm income.
Teagasc says only about a third of farms are now economically viable.