The research approach of multi-grounded action research (MGAR) is presented and analyzed. This is based on a review of issues and concerns in information systems action research. MGAR builds on the epistemological principles of multigrounding. This combines empirical, theoretical and internal grounding. The multigrounded approach builds on elements from grounded theory; i.e. building theory inductively from data through coding procedures, but it also comprises an abductive use of extant theory. MGAR is described through six knowledge contributions: (1) the MGAR process model, (2) the MGAR knowledge model, (3) the MGAR theory model, (4) the principle of the multi-grounded change outcome, (5) the principle of the multi-grounded theory outcome and (6) the principle of mutuality of purposes. MGAR has been applied in an IT service management (ITSM) case, which serves an illustration and a validation of MGAR. In this MGAR case, the improvement of ITSM has been conducted and studied through a multi-organizational setting. In the case, there was a special focus on the service quality of IT services and the relations between service providers and customers.