Background: Frozen embryo transfer (FET) has been increasingly used due to advancements in cryopreservation techniquesand the safety advantages. This study aims to determine various factors influencing the successful FET.Materials and Methods: Retrospective cohort analysis included 1112 women who underwent programmed FET betweenJanuary 2012 and October 2022, at King Chulalongkorn Memorial Hospital, Thailand. Patient characteristics, embryocharacteristics, endometrial preparation protocol, endometrial characteristics (thickness, pattern), embryo transferprocedure (tip and flow during transfer, embryo placement location, the difficulty of the procedure, presence of bloodand mucous at catheter), and operator factor were analyzed. Multiple logistic regression analysis was used to assess therelationship between collected variables and successful embryo transfer which is defined by clinical pregnancy.Results: The overall clinical pregnancy rate was 34.2%. Women aged 35-40 years and >40 years were less likelyto have a clinical pregnancy compared to those aged