The announcement was made by the planning minister said on Tuesday.
The economy expanded by 4.6 per cent in 2012 and the government had expected growth of 5 per cent in 2013.
"This was lower than what was expected," Cabinet Secretary for Planning Anne Waiguru told a news conference.
The government has previously forecast economic growth of 5.8 per cent this year.
The minister said the disappointing 2013 performance was driven by slower growth in the vital agricultural sector due to drought. The sector grew 2.9 per cent in 2013 compared to revised growth of 4.2 per cent a year earlier.
Kenya relies heavily on exports of agricultural produce, such as coffee and tea. Coffee output was down 20 per cent last year, contributing to a drop in total exports last year.
The minister also said high lending rates dragged down overall economic performance in 2013.