Introduction: Pregnancy is a period in which there are many physical, hormonal and emotional changes in the health status of pregnant women and have a significant impact on the health-related quality of life. The purpose of this study was to determine the effect of childbirth preparation classes on health-related quality of life in pregnant women. Methods: This was a semi-experimental interventional study that was carried out on 80 pregnant women referring to Sina hospital in Karoon city, Iran. Selection of samples was purposeful. For the intervention group, childbirth preparation classes were held in eight sessions from 20th week of pregnancy. The control group only received routine prenatal visits. At the end of pregnancy, quality of life was measured by SF36 questionnaire and compared in two groups. Results: According to the findings of this study, the intervention group had a significantly better score of quality of life in comparison with the control group. The intervention group received higher scores in terms of general health, physical function, physical pain, mental health, limitation of movement due to emotional problems and social function than the control group. Other dimensions including limitation of movement due to physical problems and feeling of jolly were statistically similar in both groups. Conclusion: Improving the information and knowledge of mothers in the form of holding childbirth preparation classes can improve the health of mothers and their quality of life. In order to achieve the health of mothers, it is better to more focus on the dimensions of limitation of movement due to physical problems and Feel jolly.