The plant's previous mark was 98.2 TWh, a record established in 2011-12. In 2012-13, Itaipu produced 98.63 TWh.
In April 2013, the hydroelectric project was already on pace to a record-breaking year, having broken a 2009 record in production with a first quarter output of 8.86 TWh.
Located on the Parana River between the borders of Brazil and Paraguay, the Itaipu complex met 16.9 percent of Brazil's demand and 75 percent of Paraguay's demand in 2013, the company said.
Itaipu is the world's second largest hydropower plant, trailing on China's Three Gorges in overall capacity.