John Hancock Preferred Income Fund is a closed-end, diversified management investment company. Its primary investment objective is to provide a high level of current income consistent with preservation of capital. The fund's secondary investment objective is to provide growth of capital to the extent consistent with its primary investment objective. It seeks to achieve its investment objectives by investing in securities that may be undervalued relative to similar securities in the marketplace. The fund's principal investment strategies include investing a majority of its assets in preferred stocks and other preferred securities. Its portfolio composition consists of U.S preferred securities, common stocks, foreign preferred securities, corporate bonds, and short-term investments.