Investors even as old as 50 should mostly be in the stock market, he said. That advice runs counter to conventional asset allocation wisdom that long-term investors should have a portion of their portfolios in bonds.
Even with stocks at around record highs, people who buy into the market now will do better in equities than bonds over time, Fink said. BlackRock is still "quiet bullish" on equities at these levels, he added.
Those comments about stocks versus bonds echo what billionaire investor Warren Buffett told CNBC earlier this week.
The Berkshire Hathaway chairman and CEO reiterated what he's said for years: Don't buy bonds, stock are the way to go.
Despite that advice, investors did indeed pour into bonds in the latest quarter, Fink said.
He believes that's happening because people are not good at market timing and therefore seek the safety of bonds.
Fink, BlackRock's chairman and CEO, also said the Republican tax overhaul law is largely going to help Americans, and should add about 1 percent annually to economic growth, at least in the first few years.
Meanwhile, the U.S. corporate tax cut is a problem for Mexico because the rate is now lower in America, Fink said. Companies that had domiciled in Mexico for tax reasons are going to make their new tax homes in the U.S., he predicts.
He appeared Friday on "Squawk Box" shortly after BlackRock, the largest asset manager in the world, reported quarterly earnings and revenue.
Total assets under management stand at nearly $6.3 trillion, slightly ahead of estimates.