Sigma-1 receptor (Sig-1R) is expressed at endoplasmic reticulum (ER) membranes, where it regulates a variety of specific physiological functions. However, the profile and exact roles of ER stress-related molecules after Sig-1R agonist treatment in an in vivo stroke model are largely unknown. The aim of this study is to investigate the effect of a novel Sig-1R agonist, aniline derivative compound (Comp-AD), on the ER stress response following ischemic stroke. Male C57BL/6J mice received transient middle cerebral artery occlusion for 90 min, and were then treated with vehicle saline or Comp-AD at reperfusion. At 3 hr, 1 day, and 7 days after reperfusion, immunohis- tochemistry was performed for Sig-1R and ER stress-related proteins including phospho protein kinase RNA-like endoplasmic reticulum kinase (p-PERK), phospho inositol requiring enzyme 1α (p- IRE1α), and activating transcription factor 6 (ATF6). Neurobehavioral analysis showed improved functional recovery at 1 day and 7 days after reperfusion, and the infarct volume was significantly smaller at 7 days (p < .05), in the Comp-AD group compared with the vehicle group. Comp-AD treatment upregulated Sig-1R immunoreactivity at 3 hr and 1 day (p < .05), and reduced p-PERK and p-IRE1α expression at 1 day (p < .05, respectively), in the peri-ischemic region compared with the vehicle group. Treatment with the novel Sig-1R agonist Comp-AD was neuroprotective after transient middle cerebral artery occlusion, and was associated with upregulation of Sig-1R and a reduction of ER stress.