But the Appaloosa Management founder said on "Squawk Box" he sold some shares on the spike higher.
Shares of the Snapchat parent, which were down about 2 percent before Tepper's comments, turned positive in premarket trading afterward. In early trading after the opening bell, the price was up about 2 percent to $21.87 a share.
"When I bought it, I talked to the underwriters. I said if the thing gets up into the high $20s I'm going to have to sell it," he said.
Tepper said he still believes in the hold Snapchat has on the younger generation.
"My youngest daughter loves the thing. Anybody between 12 and 25 loves it," he continued. "It's kind of anti-Facebook in that generation, too."
"I don't really use it myself. But I will be forced to use it" eventually, he said.
Snap surged 44 percent last Thursday from its IPO price of $17 per share, closing at $24.48. The stock surged again on Friday.
"Up near $30, it's too high for right now. One day it may be $30. One day it may be $100," Tepper said. "I can't love stocks at every price."
On Monday and Tuesday, Snap stock tanked.
Tepper said he might be willing to buy more Snap if the stock were to get down near the offering price again. "I would love to buy the stock there."
"I'm a believer in the company," he reiterated. "It's a valuation question to me. I'm in a nowhere land on valuation here" for Snap at current prices.
Tepper's Appaloosa has $17 billion in assets under management.
(Disclosure: CNBC parent NBCUniversal is an investor in Snap.)