[4] Hollub officially became president and CEO of Occidental Petroleum in April 2016,[4][5][10] with responsibility for operations, strategy and financial management.

[4] The appointment made her the first woman to head a major American oil company,[1][2][3][6][7][9] and that year Fortune named her #32 on its annual list of the Most Powerful Women in business.

[6] Under Hollub, Occidental cut production costs in response to falling crude prices[6][8] but decided not to lay off employees.

[7][13] The company focused on existing core operations in the Middle East, the United States, and Colombia in Latin America,[8][14] while continuing to sell low-yield fields in Iraq, Libya, Yemen, North Dakota, Colorado, Kansas, and Oklahoma.

At that time, Forbes wrote that Hollub's focus on high-producing oil fields had made Occidental "leaner" and "poised to gusher cash for the next half-century.

[17] In March 2020 amid a major stock market crash and an international oil crisis that saw the company's stock price plummet dramatically, a group of activist investors led by Carl Icahn have stated their desire to replace the entire Occidental board of directors, including Hollub.

[23] Hollub is a longtime fan of her alma mater's Alabama Crimson Tide football program, particularly under former coach Bear Bryant.