Pyroptosis is a type of programmed cell death, which has been associated with multiple inflammatory diseases including diabetic atherosclerosis (DA). This study aims to explore the role of sinapic acid (SA) in the pyroptosis of macrophages in DA. Our results from the in vivo experiments showed that low-dose (≤50 mg/kg) chronic SA administration suppressed serum endothelin 1 (ET-1) and interleukin-1β (IL-1β) contents, pyroptotic death of bone marrow–derived macrophages, and the expression of pyroptotic proteins ASC, NRLP3, and caspase-1. Besides, lncRNA-metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was robustly upregulated in the macrophages of rats with DA and could be lowered by low-dose SA administration. Gene overexpression and knockdown experiments showed that MALAT1 had a modestly positive effect on the pyroptosis of normal macrophages. Moreover, in macrophages incubated with high-glucose and Ox-LDL, 1-μM SA treatment displayed a suppressive effect on the cell pyroptosis similar to that of MALAT1 knockdown. Transfection of the pcDNA-MALAT1 expression vector counteracted the decrease in MALAT1 expression and macrophage pyroptosis caused by SA. In conclusion, low-dose SA can abate the pyroptosis of macrophages by downregulation of lncRNA-MALAT1 in rats with DA.