There is growing concern surrounding the detrimental effect of term-time employment on university students’ academic success. The narrow focus of previous studies has resulted in the literature being characterised by mixed results. This study sought to clarify the effects by comprehensively investigating and controlling for a large number of variables across a diverse range of university students (N = 1841). Students completed an online survey during the first semester of study (2010) and their responses were later matched to their academic records for that semester. The results show that the majority of working students reported working out of financial necessity. There was no difference in grades between employed and non-employed students; however, hours worked had a direct negative linear effect on the grades of employed students. Analysis indicated that employed students would have had significantly higher grades than the non-employed subsample, if they had not worked during term. The variable ‘reported negative effects of work on study’ partially mediated the effect of hours worked on grades. Studying engineering moderated the effect; when engineering students worked, the negative effect on grades was greater than for those studying other subjects. In addition, hours spent in employment partially mediated the effects of age, debt and financial pressure on GPA. Students also reported that work affected other areas of their life (time spent socialising/relaxing, in leisure/sport, sleeping and with family). Just over a fifth of the working students reported feeling that the university did not make it possible to combine work and study. These findings have implications for students, student supporters and academic institutions. Students should be aware of the negative effects of work on academic performance and seek to minimise the amount they work. Supporters may be able to relieve financial pressure on students, encourage realistic perceptions about students’ financial needs, and encourage students to limit the number of hours they work. Finally, academic institutions can also assist students in balancing work and study by providing a flexible learning environment.