Heat stress threatens maize production. Through a genome-wide association study using pollen viability decline rate as a phenotype, we identified ZmHEAT1, encoding ZmKAKU41, a nuclear envelope protein known to regulate nuclear morphology in both maize and Arabidopsis, as a key regulator of thermotolerance. ZmHEAT1 positively regulates heat tolerance at seedling and reproductive stages, with its overexpression improving thermotolerance and its knockout reducing pollen viability and yield under high temperatures. ZmHEAT1 interacts with its homolog ZmKAKU42 and the nucleoskeleton protein ZmNCH1 to form a complex at the nuclear envelope. Mutants lacking ZmHEAT1 or ZmKAKU42 exhibit increased nuclear envelope damage under heat stress, along with repressed expression of key heat shock protein genes HSP90-2 and HSP17.4. This work establishes the ZmHEAT1/ZmKAKU42-ZmNCH1 complex as a critical guardian of nuclear integrity and a modulator of the heat-responsive transcriptional program, providing a valuable genetic resource for breeding heat-tolerant maize.