Infections are among the most common complications after transplantation and greatly increase the morbidity and mortality of transplantation and decrease graft survival. This chapter describes a timeline of infection after transplantation. Post-transplant infections can be mitigated by preventative methods, routine vaccinations, intake of clean food and water, preventative measures during times of outbreaks visits with travel medicine specialists prior to visiting high risk regions, safer sexual practices for non-monogamous recipients, and guidance on better tattoo acquisition. Hepatitis viruses are common causes for liver transplantation and also common complications after transplant, predominantly as reactivation of latent infections. Molecular diagnostics are emerging as a diagnostic methodology for bacterial infections. Invasive fungal diseases, particularly aspergillosis, are significant causes of morbidity and mortality in transplant recipients. Treatment of individual parasitic infections can involve medications that may interact with transplant medications, or have significant side effects, and should be used carefully.