The transition to parenthood creates new responsibilities for couples that can always be challenging,especially if this happens at an older age.Therefore, the aim of this study was to examine the lived experiences of men between40and45years old in the context of transitioning challenges to parenthood.The methodology of this study was qualitative and with a phenomenological approach.The study population was men between40 and 45years old in Hamedan who experienced fatherhood for the first time in2023or2024and whose children were under two years old.A sample of14people was selected from them through purposive sampling, and the sampling process lasted until saturation was reached.The data collection method was semi-structured interviews.The collected data were analyzed using member checking, audit trail, and inter-coder reliability methods.After analyzing the data,12 subthemes and 5 main themes were obtained, including individual barriers to fatherhood experience, differences in parenting approaches, need for social and family support, career challenges, and concerns about the generation gap and relationship with the child.The results of the research, in addition to creating insight and awareness of the challenges of men who have become fathers for the first time between the ages of 40and45.can be used to plan to address the problems and challenges of this group of fathers.