The $285.6 billion fund also in January increased its exposure to U.S. government and Treasury-related securities, which include U.S. Treasury notes, bonds, futures, and inflation-protected securities, data from the firm's website showed on Monday. PIMCO increased its Treasury holdings to 30 percent from 26 percent, the most since July.

The PIMCO Total Return Fund decreased its exposure to mortgages, its largest holding, to 37 percent in January--the lowest since August 2011--from 42 percent in December, after hugely profitable bets last year. The PIMCO fund was up 10.36 percent in 2012, surpassing 88 percent of peers.