Fieldwork is an important part of higher education programmes in geography, geology, environmental sciences and biosciences because it offers opportunities to enhance graduate employability alongside pedagogical and social benefits. However, not all students choose to participate in fieldwork and the reasons that some opt out are unknown. We used the expectancy-value theory of motivation to investigate why some students opt out of fieldwork. Data from six universities showed that students who opted out held lower fieldwork motivation than those who opted in. There was no effect of gender on fieldwork motivation but there was an effect of previous experience whereby students with previous fieldwork experience had higher motivation than those without. The reasons that students opted out related to pursuing alternative opportunities, barriers to their participation or a disinterest in fieldwork. Our findings suggest that alternative opportunities should offer similar pedagogical and professional and social development benefits to fieldwork and that further fieldwork opportunities are included in programmes to cater for students who have high fieldwork motivation but encounter barriers that prevent them from participating in field courses. Furthermore, programme design should eliminate structural barriers to fieldwork participation.