Internships offer the opportunity to gain experience and skills by working in organisations or to establish a professional network, and there is empirical evidence of the positive effects of practical experience in higher education. However, there are only a few studies on the characteristics of workplace tasks that facilitate learning during internships. In this paper, we address this research gap by conducting a diary study to examine students' work tasks at the beginning and end of an eight-week business internship period, their perceptions of the tasks, and the influence of task characteristics on self-perceived learning. Analyses of approximately 2,000 work tasks documented by 51 students show that the frequencies of different work tasks did not differ substantially between the first and last week of the business internship. At both times of data collection, many students were engaged in organisational routine and administrative tasks, especially those with a domain-specific focus. However, the values for the assessment of task characteristics (such as challenge/difficulty) were higher at the beginning of the internship than towards the end. Causal analyses revealed that task characteristics such as novelty or feedback (from colleagues or supervisors) were positive predictors of self-perceived learning during both weeks, whereas the predictive power of other task features changed. For example, help received (from colleagues or supervisors) was a significant predictor in the first week of the internship but not in the last; the opposite was the case for autonomy. From these results, we derive implications for both future research and the active design of internships in the higher education context.