The effect of the COVID-19 pandemic on doctoral students' research productivity is examined with a special focus on gender, parenthood, and the personality trait conscientiousness. Data consist of 614 doctoral students active in medicine, technology, the natural sciences in Sweden. Results indicate that the overall research productivity of doctoral students has increased during COVID-19. It is tested if the observed increase in research productivity depends on gender, parenthood, or conscientiousness. Hypotheses regarding a pandemic penalty for women and parents are not supported. However, results indicate that conscientiousness had a positive effect on doctoral students' research productivity during the pandemic. It is concluded that conscientiousness has been an important factor in determining the research productivity of doctoral students during COVID-19. The results are discussed with regard to the national context of Sweden, where schools, childcare facilities, and laboratories were open to a larger extent during COVID-19 compared with many other countries.