Innovative behavior (IB) is an important issue in academic and other sectors. The increasing uncertainty caused by COVID-19 has resulted in rising job insecurity for employees in the e-commerce industry. This has jeopardized career sustainability (CS). Numerous studies have explored the influence of supportive leadership (SL) on IB, but so far there is still a dearth of research investigating the role of CS. In addition, CS must be considered because the perceived sustainability of a career has an impact on individual innovation. Therefore, based on job demands-resources (JDR) theory, we analyzed the effects of SL on IB as well as the roles of CS in IB. The mediating role of employee’s perceived occupational sustainability was explored. This study investigates the associations between supportive leadership style (job resource) and employee innovative behavior (job demand). In total, 308 valid samples were collected from China. Structural equation modeling examines the construct validity and path relationships. The results show that in China’s e-commerce industry, under the uncertainty brought about by the COVID-19 pandemic, only when employees perceive CS can SL promote the transformation of job resources into workplace IB. That is, CS completely mediates SL and IB. This provides new information for the management of employee behavior in the current special period. The result revealed that SL improves IB through CS. Theoretically, this study fills the gap and establishes a theoretical framework for SL and IB. Practically, we offer guidance for enterprises and managers in that they should provide their employees with work resources which are good for employee CS so as to promote employees’ IB.