The adoption of multi-channel strategies by retailers, encompassing both online and offline modalities, has fundamentally transformed consumer shopping behaviors, resulting in a significant increase in mobile shopping. Nonetheless, the long-term success of mobile shopping apps is heavily dependent on consumers' continuous use. Regrettably, the existing studies on this area remain vague and require further exploration. This study aims to close this gap by examining Malaysian consumers' continuance intention and continuance use of mobile shopping through the lens of ISSM in the context of mobile shopping apps. We utilised a quantitative approach and successfully collected 369 responses from Klang Valley, using purposive sampling techniques. The predictive hypotheses developed were validated using Partial Least Square -Structural Equation Modelling (PLS-SEM) and were further supplemented with Necessary Condition Analysis (NCA) to determine must-have factors based on necessary logic. The PLS-SEM results confirmed the association between continuance intention and continuance use. The findings revealed that service quality and system quality are associated with satisfaction, but not information quality. Additionally, service quality, system quality, and information quality, together with satisfaction, trust and incentive have a positive significant influence on Malaysians' mobile shopping app continuance intention. However, the NCA results indicated that system quality is the sole must-have factor that contributes to satisfaction. Meanwhile, service quality, system quality, information quality, satisfaction, trust, and incentive are the must-have predictors for mobile shopping app continuance intention. The study sheds light on previously unexplored aspects namely, continuance intention and continuance use, within the framework of the ISSM in the context of mobile shopping. By doing so, it offers more refined and actionable insights to improve consumer experience and foster sustained engagement with mobile shopping apps. Simultaneously, it contributes to the advancement of knowledge regarding the foundational constructs and their interconnectedness, thereby enhancing theoretical development in this domain.