The non‐canonical inflammasome sensor caspase‐11 and the pyroptosis executor gasdermin D (GSDMD) are known drivers of inflammation and pyroptosis, a type of regulated immunogenic cell death known to favor cell mediated immunity (CMI) in the context of cancer, infection, and autoimmunity. However, the role of the noncanonical inflammasome components and pyroptosis has not been addressed in the context of vaccine adjuvant induced immunity. Here we show that caspase‐11 and GSDMD are essential for the induction of CD8⁺ and Th1   responses by polymeric nanoparticulate adjuvants. We reveal a division of labor for IL‐1 family cytokines where   IL‐1 supports Th1 responses, whereas IL‐18 promotes CD8⁺ T cell responses. We show that particles induce   reactive oxygen species (ROS) in a size‐dependent manner which is essential for promoting CMI after vaccination. We identify nanoparticles in the 50‐60nm range as optimal adjuvants for the induction of ROS, GSDMD activation and long‐lived and protective Th1 and CD8 responses. Exploiting size as a key attribute, we   demonstrate that biodegradable nanoparticles made of the FDA‐approved polymer poly‐lactic co‐glycolic acid   (PLGA), are potent CMI‐inducing adjuvants for protein antigens. Our work implicates ROS, activation of the noncanonical inflammasome and associated effector molecules in the mode of action of polymeric nanoparticulate   adjuvants and establishes size as a key design principle for the development of novel adjuvants for vaccines   against cancer and intracellular pathogens.