"I'm pretty optimistic the margins will continue to expand," he said. "Ever since what I call the 'trauma of 2008,' companies—even five years into this expansion with record profits and cash flow—are operating like it could happen again. And they're keeping a lid on their costs, which means they're hiring very judiciously and expanding very slowly."
Yardeni said that he wasn't a fan of predictions of when the Federal Reserve would reduce its $85 billion-per-month bond-buying program.
(Read more: I'm sorry for QE, former Fed official says)
"I'm getting a little tired of tapering, all the tapering chatter, but we've got to deal with it," he said. "It's an ongoing issue."
But Yardeni was also wary of stocks running up too fast.
"The main issue is whether this is going to lead to an asset bubble," he said. "My biggest fear is we get to over 2,000 in the next couple of months."
—By CNBC's Bruno J. Navarro. Follow him on Twitter