Walmart’s chief executive, Doug McMillon, was named chairman of the Business Roundtable trade group.

Mr. McMillon replaces Jamie Dimon, chief executive of JPMorgan Chase, and will serve a two-year term starting Jan. 1, the C.E.O. group said on Thursday.

A pledge by top C.E.O.s to work for more than shareholders drew criticism in August from investor activists, who accused them of contradicting their inclusive message by lobbying against social and environmental reform efforts.

The activists faulted the roundtable for taking a public stand that corporations should seek to promote the interests of a wide range of stakeholders, including workers and communities, while pressing for such rule changes as making it harder to file proxy resolutions.