"Tim Sloan has my faith," said Buffett, chairman and CEO of Berkshire Hathaway. "When you find a problem, you have to jump on it."
"Somebody messed up and the job is to find out who messed up," he added in an interview on CNBC's "Squawk Box."
Berkshire is Wells Fargo's largest shareholder, holding a 9.4 percent stake.
When asked whether he sold any shares of Wells Fargo, Buffett said "only enough to stay under 10 percent, which was something the Fed requires."
On Tuesday, Wells CEO Tim Sloan will appear before the Senate Banking Committee. In prepared testimony, Sloan apologized for the creation of unauthorized accounts and said the bank has hired back more than 1,000 workers who were wrongly fired or left under a cloud.
In late August, Wells admitted that as many as 3.5 million accounts were created for customers without their permission. That's nearly 70 percent more than originally thought. The scandal led to the departure of multiple executives, including former CEO John Stumpf.
Buffett told CNBC on Aug. 31, "There's never just one cockroach in the kitchen when you start looking around."
"You may very well find that it wasn't just the one who misbehaved that you find out about," he said.
While the practice had been going on for years at the bank, it only became public last year, when Wells agreed to pay a $185 million settlement with regulators.
Since then, it was revealed that the tactics extended to enrolling customers in auto insurance that they didn't need. Wells paid a $142 million class-action settlement and $2.8 million in refunds to affected customers.
Buffett on Tuesday joined "Squawk Box" from Omaha, Nebraska — the home of Berkshire and where Purpose Built Communities was holding its annual conference. Buffett is co-founder of Purpose Built, along with the investor Julian Robertson. The nonprofit consulting firm helps communities revitalize neighborhoods.