Objective: The role of micronised progesterone in hormone regimens for transgender individuals undergoing feminising hormone therapy remains uncertain. We aimed to determine the effect of oral micronised progesterone on sleep quality, psychological distress, and breast development in transgender individuals undergoing feminising hormone therapy. Design: Prospective case–control study. Twenty-three transgender individuals on stable oestradiol treatment newly commencing 100 mg oral progesterone (n = 23) and controls continuing standard care (n = 19) were assessed over 3 months. Methods: Pittsburgh Sleep Quality Index (PSQI), Kessler psychological distress scale (K10), and Tanner stage to assess breast development were assessed at 0 and 3 months. Non-parametric analysis of covariance was used to compare differences between groups. Results: Compared with controls over 3 months, there was no difference in PSQI (P = 0.35), K10 (P = 0.64), or Tanner stage (P = 0.42). There was no significant difference in the proportion of individuals with clinically significant improvement in PSQI (25% vs 22%, P = 0.84). One individual had a significant deterioration in psychological distress that improved following the cessation of progesterone. Conclusions: Low-dose progesterone was not associated with changes in sleep quality, psychological distress, or breast development over 3 months follow-up, though there was significant inter-individual variability. Larger, placebo-controlled trials are required to further evaluate different doses of progesterone in feminising hormone therapy regimens.