OBJECTIVE: This study was conducted to examine the effect of the online Mindfulness-Based Stress Reduction (MBSR) programme applied to pregnant women on their prenatal comfort and foetal anxiety levels. MATERIAL AND METHOD: This randomised controlled study was conducted between July and October 2022, with 89 pregnant women registered in a Family Health Centre of Adiyaman, located in the Southeastern Anatolia region of Turkey. In the study, a total of eight sessions of MBSR programme, one session per week for eight weeks, were applied to the pregnant women in the experimental group. Data of the study was collected with the 'Personal Information Form', 'Prenatal Comfort Scale (PCS)', and 'Fetal Health Anxiety Inventory (FHAI)'. Descriptive statistics, chi-square test, and t-test for independent and dependent samples were utilised in the analysis of the data. RESULTS: It has been determined that the PCS total mean score after the intervention is 58.91 ± 7.18 in the experimental group and 50.56 ± 15.78 in the control group; the post-test FHAI total mean score is 4.52 ± 1.66 in the experimental group and 9.76 ± 5.00 in the control group, and the difference between the groups is statistically significant ( CONCLUSION: It has been determined that the MBSR programme applied to pregnant women has increased the prenatal comfort levels of pregnant women and has decreased foetal health anxieties. In line with these results, it is recommended that the MBSR programme may be used as an alternative method to relieve pregnant women.