Volunteering can be a catalyst for career development, yet little is known about the specific skills event volunteers acquire or the personal and situational factors that shape these outcomes. This research assessed skill development in 545 volunteers at a major sporting event in North America. Using a mixed-methods approach, we analyzed qualitative and quantitative survey data. Qualitative analyses identified 12 skill themes divided equally into ‘soft skills’ (adaptability, communication, thinking, relationship building, work ethic/professionalism, and work management) and ‘hard skills’ (professional expertise, specific language and communication proficiency, knowledge of sport, management and operations, innovation and technology, and manual labor). Quantitative analyses revealed the total number of skills developed depended on volunteers' motives and levels of supervisor support. High supervisor support offset the effects of low motives on volunteer skill development.