McDonald’s Corp.’s new CEO is determined to make changes at the top to move the company away from a culture that tolerated partying and fraternizing between some senior managers and rank-and-file employees.

Chris Kempczinski, the new chief executive, is seeking to restore a more professional culture at McDonald’s after what some current and former employees described as an environment influenced by his predecessor’s late-night socializing with some executives and staffers at bars and flirtations with female employees. Mr....