Previous research has demonstrated the benefits of peer feedback for improving student work. Gender, as an individual characteristic, is now receiving increased attention due to its influence on the peer feedback process. This study examined the effects of gender and peer assessment training on the amount and content of peer feedback provided by assessors for poor, average and excellent writing samples, using a randomised controlled design. A total of 240 undergraduate psychology students participated in the study. Half of the participants received peer assessment training, while the other half received task instructions only. Participants were assigned to eight subgroups, providing peer feedback to writing samples attributed to fictitious male or female assessee. Analysis of 3017 feedback segments revealed that women provided a greater amount of peer feedback compared to men. Women also offered more positive verifications and suggestive elaborations for average and poor writing samples. Male assessees received more suggestive elaborations, while trained assessors provided more positive verifications. These findings suggest the need for a multifaceted training programme to bridge the gap between gender-based differences in peer feedback characteristics.