From 1980 to 2006, downsizing and reengineering of organizations reduced workforce and middle management levels within 90% of the Fortune 100 businesses. Downsizing may have changed the required knowledge and skills needed by remaining middle managers in their restructured roles. The purpose of the qualitative case study was to determine the core competencies of middle managers in the 21st century. Content analysis methods analyzed peer-reviewed literature from the EBSCO databases. Evidence purported the presence of specific core competency skills required of successful 21st century middle managers. Evidence indicated middle managers should prioritize or emphasize process skills over personal skills. Process skills are execution proficiencies needed by middle managers to enact actions and changes versus personal capabilities associated with interactions, preparations, and planning. Additionally, the study presented evidence of specific middle manager skill sets for organization, team, and individual contexts.