The relationship between large-group classroom attendance by students and test achievement in problem-based learning (PBL) curricula is unclear. This study examined the correlation between attendance at resource sessions (hybrid lectures in the PBL curriculum) and test scores achieved in pharmacology and determined whether the score achieved was related to student gender. A cross-sectional observational study over one academic year of 1404 pre-clerkship medical students was performed. Class attendance during pharmacology resource sessions and MCQ test scores achieved in pharmacology were analysed. The percentage of students’ attendance in resource sessions declined over three years of the programme, from 78.7 ± 27.5 in unit I to 22.1 ± 35.6 (mean ± SD) in unit IX. A significant but weakly positive correlation was evident between attendance and achievement in pharmacology (r = 0.280; p < 0.0001). The mean score of the students who attended > 50% of the resource sessions was significantly higher (p < 0.0001). Students who attended ≤50% were more likely to achieve lower tertile scores. The mean score achieved and the number of higher tertile scorers were higher among students who attended > 50% of the resource sessions. Although female students’ attendance was significantly higher, no significant gender-related differences in either mean scores or top grades achieved were found. In a PBL curriculum, the classroom attendance of students in pharmacology declined during the pre-clerkship phase. A weak positive correlation was found between attendance and academic achievement, as measured by MCQ test scores. Factors other than motivation and attendance may confound gender-based academic performance and merit further research.