Upstart Managers School Sage of Omaha

The pupils are beating the master at Warren Buffett-led Berkshire Hathaway Inc.

Two investment managers, hired by the 83-year-old billionaire in recent years as part of his succession plan, each posted returns last year that outdid both Mr. Buffett's performance as Berkshire's top stock picker and the Standard & Poor's 500-stock index, according to people familiar with the matter.

The 2013 returns mark the second year in a row that the two men beat the broader market gauge, which gained 32% including dividends last year, as well as their boss. The people wouldn't say by how much the two outperformed the market in 2013, but the year before, they each beat the S&P by a double-digit margin, Mr. Buffett said in his 2012 annual letter to shareholders.