The investor told CNBC that he started to acquire the share, which is now equivalent to a 5.5 per cent stake, in March.
Mr Buffett said that the percentage is worth 64 million shares with the majority acquired during the third quarter of 2011.
The move represents a change in direction for the investor who has previously refused to invest in the IT industry claiming that it is too difficult to predict what might happen in the future.
In the interview Mr Buffett said: âIf you're in some country around the world and you're developing your IT department you're probably going to feel more comfortable with IBM than with many companies."
He said that he started to look into buying IBM stock after reading the firm's annual report last year.
The so-called âSage of Omahaâ paid an estimated $170 per share when making the investment, a lower figure than the approximately $187 the shares were priced at last week.
By Jim Ottewill