Mitochondrial fusion and fission dynamics fine-tune cellular calcium homeostasis, ATP production capacity and ROS production and play important roles in cell proliferation and migration. Dysregulated mitochondrial dynamics is closely related to tumor development, but the mechanism of mitochondrial dynamics dysregulation and its role in the development of lung cancer remains unclear. Here, we demonstrate that the DNA sensor protein absent in melanoma 2 (AIM2) is highly expressed in non-small cell lung cancer (NSCLC) cells and that high AIM2 expression is associated with poor prognosis in patients with NSCLC. High expression of AIM2 contributes to tumor cell growth and proliferation independent of inflammasome activation in vitro and in vivo. Further studies have shown that AIM2 colocalizes with mitochondria in NSCLC cells and that AIM2 knockdown leads to enhanced mitochondrial fusion and decreased cell proliferation. Mechanistic studies have shown that AIM2 downregulation promotes MFN2 upregulation, thereby enhancing mitochondrial fusion. Moreover, we found that mitochondrial fusion driven by AIM2 knockdown leads to a decrease of cellular reactive oxygen species (ROS) production, which further causes inactivation of the MAPK/ERK signaling pathway. Together, we discovered a novel function of AIM2 in promoting NSCLC development by regulating mitochondrial dynamics and revealed its underlying mechanism. Our work provides new intervention targets for the treatment of NSCLC.