A protective case is provided for receiving and supporting a medication infusion pump of the type used to deliver a selected medication such as insulin to a patient. The protective case comprises a transparent housing of impact resistant material for slide-fit reception of the pump, in combination with a seal cap for removable mounting onto the housing to define a substantially waterproof pump enclosure. The seal cap is formed from a resilient shock absorbing material and cooperates with additional shock absorber elements to resiliently support the pump within the housing. A catheter port is formed in the seal cap for sealed passage of a catheter tube extending from the pump to the patient. A belt clip is removably mounted onto the assembled case to prevent seal cap separation from the housing, and to provide a convenient structure for belt mounting of the protective case onto the body of patient.