U.S. stock mutual funds and ETFs accounted for $25.2 billion of the total cash gains, the most since January 2004. Global mutual funds and ETFs overtook them with inflows of $29.8 billion, a monthly record according to the research company.

The total inflows into stock funds surpassed the previous record of $53.7 billion in February 2000, TrimTabs said.

The benchmark S&P 500 stock index has risen 5.4 percent so far this month. Analysts have cited this month's strong inflows as a support to stock markets, along with stronger-than-expected corporate earnings and U.S. lawmakers' deal to avert the "fiscal cliff" of tax hikes and spending cuts.

According to Thomson Reuters' Lipper service, which tracks only funds that are based in the U.S., the three weeks ended January 23 have seen the biggest inflows from retail investors into stock funds since the start of 2001. The latest three-week streak has brought $14.9 billion into stock mutual funds alone, while the streak ended in early 2001 brought $16.3 billion into the funds.

Investors gave $6.1 billion to U.S. stock mutual funds and ETFs in the past five trading days alone, TrimTabs reported. Global funds, meanwhile, pulled in $9.3 billion over that period.