The yield on the 182-day Treasury bill also nudged lower in the same auction to 10.367 percent from 10.377 percent last week.
The bank said it received bids worth 16.7 billion shillings ($183 million) for a total of 6 billion shillings worth of bills on offer.
It accepted 11.7 billion shillings. Next week, the central bank will offer bills of all maturities worth a total 8 billion shillings, it said.