Infertile women often experience chronic stress that can harm their well-being. Our aim was to investigate the effect of mindfulness-based stress reduction programmes on tolerance of ambiguity, rumination, and metacognitive awareness in infertile women. The sample included all infertile women referred to the Valiasr Hospital Health Center in Iran in 2019 who were treated for infertility. A total of 52 women undergoing infertility treatment were selected by availability sampling and assigned to either the experimental (26) or the control group (26). Using multivariate analysis of covariance (MANOVA) we found that a mindfulness-based stress reduction programme helps to increase tolerance to ambiguity, rumination, and metacognitive awareness among infertile women.