A day after reports surfaced that activist investor Kimmeridge Energy Management Co. LLC had taken a stake and was pushing for change, Chesapeake Energy Corp. CEO Nick Dell’Osso said Thursday he agreed the company is undervalued.

Reuters initially reported that Kimmeridge took a 1.6% stake in the Oklahoma City-based independent, putting it among the largest shareholders. The private equity firm is reportedly pushing to enhance value, partly by divesting oilier assets in favor of natural gas.

Dell’Osso during the first quarter conference call said management also believes shares are undervalued. Chesapeake kicked off a $1 billion share buyback program in the first quarter. He added that the buyback program could soon be exhausted “given the current valuation of our...