The star of films such as "Ted," "Friends With Benefits," and the TV series "That 70s Show" told CNBC in London: "I've just started investing in stocks, which is new for me."
"I'm an advocate of like put things in the bank, put it in a CD (a certificate of deposit), lock it away, be safe. And I've been pushed kind of forward to take chances and then learning a little bit about the stock market and companies," she said.
Her words sparked a lively response on Twitter. Financial Acrobat, a trader, consultant and tweeter of financial news, warned that it could be a contrarian signal.
"When people like @FoxonStocks and @RealMilaKunis start talking stocks, we are normally at the very end of a bull market."
Kunis' move comes as the Dow Jones Industrial Average reached an all-time high and logged its first 10th-straight winning streak since 1996 at the close on Thursday. The S&P 500 remains within a hair's breadth of its own record.
Kunis, however, remained coy about what stocks she's investing in, responding with a firm "no" when asked what's in her portfolio.
(Read More: How Soon Will the S&P Hit 1,600?)
Barry Ritholtz, director of equity research at Fusion IQ, tweeted that he was glad she was sticking with her movie career: "If she was giving up acting to become a daytrader, we'd have great contrary indicator!"