M3, the broadest measure of money circulating the Bahraini economy, was 7.79 billion dinars ($20.67 billion) at the end of January compared with 6.69 billion dinars a year earlier, the central bank said in a monthly report on its website.
Annual growth in money supply fell from 21 per cent in December and was the slowest rise since March 2007.
As in other states in the world's biggest oil-exporting region, Bahrain's money supply surged as oil prices rallied to a peak last July above $147 a barrel.
Oil prices have since fallen more than $100 a barrel and rapid economic growth in the Gulf has come to an end as the region suffers the fallout of a global financial crisis that has sent much of the industrialised world into recession.
Citing a decline in inflation, Bahrain's central bank on Tuesday cut the amount of reserves that banks are required to hold to 5 percent from 7 percent, a measure analysts said was designed to unlock credit markets.
Money supply in January fell from 7.98 billion dinars in December.
Cash held in time and savings deposits rose 13.7 per cent, down from growth of 17.5 per cent at the end of last year, the data showed. Demand deposits grew 14.8 per cent in January.
The central bank's net foreign assets rose to 1.29 billion dinars in November from 1.2 billion dinars a month earlier, the data showed.
Claims on the private sector in November rose to 6.27 billion dinars from 6.23 billion dinars in October.