Background The levonorgestrel intrauterine system and copper T are effective, long-acting intrauterine contraceptive devices (IUDs) for women. Use-related adverse events have led to premature removal of the method in our environment. LNG-IUS is expected to reduce use related adverse events more effectively than copper T IUD. There is a need to determine the safer method amongst the two devices to enable counselling and help users make informed choices. Research design The study was a comparative cohort study Aim and objective The aim of the study was to compare the efficacy and safety of LNG - IUS and Copper T380A IUDs in Ibadan. Methodology The study was a comparative cohort study involving 100 healthy women within age group 18 – 44 years that visited the family planning clinics in Ibadan seeking contraception. Purposive sampling technique was employed. The participants were recruited until sample size was achieved. Written informed consent was obtained followed by documentation of baseline characteristics. The insertions were carried out in the interval period during menstruation. Prior to insertion, about 5 ml of venous blood was collected from each participant and at the 3rd, 6th, 9th and 12th months post-insertion for laboratory analyses. A standard pelvic examination was performed before IUD insertion under asepsis. Follow-up visits were scheduled at three, six, nine and twelve months post-insertion. Those with complications were seen as they presented at the clinic by the principal investigator