Revenues were estimated at 608 billion riyals ($162 billion), well below projections and 2014 income, while spending came in at 975 billion riyals ($260 billion), ministry officials announced at a press conference in Riyadh.
The budget deficit is the highest in the history of Saudi Arabia, the world's largest oil exporter, but was not as big as some expected.
The International Monetary Fund had projected the 2015 deficit to be around $130 billion and other reports also put it above $100 billion.
It was the second deficit year in a row for Saudi Arabia and Riyadh is expected to announce another shortfall when it unveils its 2016 budget later on Monday.
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The kingdom has seen a sharp drop in revenues as oil prices have fallen by more than 60 percent since mid-2014 to below $40 a barrel.
Public revenues are the lowest since 2009, when oil prices dived as a result of the global financial crisis.
Income for 2015 was 15 percent lower than projections and 42 percent less than in 2014.
Oil income has normally contributed around 90 percent of total revenues.
Riyadh maintained high spending this year, and launched an expensive military intervention in Yemen, by tapping into the huge fiscal reserves it accumulated when oil prices were high.