Background: Immunosuppressive therapies are vital for solid organ transplant (SOT) recipients to ensure graft survival, but long-term use can lead to complications. This study aimed to comprehensively evaluate the complications associated with immunosuppressive agents across different types of major SOTs. Methods: In a retrospective cohort study using a national claims database, we analyzed adult SOT recipients who began immunosuppressive therapy from 2007 to 2018. We identified complications such as infections, acute kidney injury, hypertensive emergencies, chronic kidney disease, hypertension, diabetes, dyslipidemia, and osteoporosis. These outcomes were determined through diagnostic codes, medication usage data, and hospital or emergency department visits. Results: Among 30,997 transplants with three-year follow up, complication rates varied by transplant type. Pancreatic transplant recipients had the lowest complication rate (225.9 per 1000 patient-years), while lung transplant recipients experienced the highest rate (823.9 per 1000 patient-years). Serious infections and chronic kidney disease were most common 2 to 6 months post transplant. Other complications, like acute kidney injury, hypertensive emergencies, hypertension, diabetes, dyslipidemia, and osteoporosis, were predominantly observed in the first month. Opportunistic infections peaked between 7 months and 1 year after transplantation. Conclusions: This study emphasizes the varied complications related to immunosuppressive therapy among different SOT recipients, delineating specific timeframes for each complication and maintenance regimen.