Backgroud: The objective of this study was to assess the psychological implications of mild ovarian stimulation combined with single embryo transfer (SET) during a first IVF cycle. Methods: We conducted a randomized controlled two-centre trial. Three hundred and ninety-one couples were randomized to undergo either mild ovarian stimulation with GnRH antagonist co-treatment and SET (n=199) or conventional GnRH agonist long protocol ovarian stimulation with double embryo transfer (DET) (n=192). Women completed the Hospital Anxiety and Depression Scale, the Hopkins Symptom Checklist and the Subjective Sleep Quality Scale at baseline, on the first day of ovarian stimulation and following embryo transfer. Affect was assessed daily with the Daily Record Keeping Chart from the first day of ovarian stimulation until the day treatment outcome became known. Results: The conventional IVF group experienced elevated levels of physical and depressive symptoms during pituitary downregulation. At oocyte retrieval, this group experienced more positive affect and less negative affect than the mild IVF group. In the conventional IVF group, cycle cancellation was associated with less positive and more negative affect. Conclusions: During the first IVF treatment cycle, mild ovarian stimulation and SET does not lead to more psychological complaints than conventional IVF.