Rationale: Diffuse low-grade gliomas (DLGGs) are relatively rare tumors that are more likely to be misdiagnosed and wrongly treated in clinical practice. We report a case of DLGG detected by computed tomography and magnetic resonance imaging (MRI).Patient concerns: A 58-year-old man suddenly phantom smells for half an hour and was previously healthy.Diagnoses: Computed tomography findings showed a leaf-shaped slightly hypodense shadow in the right temporal lobe with no obvious mass effect and an unclear boundary. MRI findings showed diffuse and slightly longer T1-weighted imaging (T1WI)/T2-weighted imaging (T2WI)signal in the right temporal lobe and hippocampus, slight hyperintensity on diffusion-weighted imaging, diffuse swelling in the right temporal lobe and hippocampus, and shallower cerebral sulci and fissures. No obvious abnormal enhancement was observed on enhanced MRI. Contrast-enhanced magnetic resonance angiography showed no obvious abnormality.Interventions: Intravenous thrombolysis with alteplase (rtPA) was given first.Outcomes: The patient had an acute and persistent generalized tonic-clonic seizure and was given antiepileptic treatment. Immunopathological and molecular genetic testing diagnosed as DLGGs. After targeted chemotherapy, the patient's symptoms improved significantly.Lessons: For those cases with clinical acute neurological impairment and imaging findings similar to those of ischemic stroke, where the distribution of lesions is inconsistent with the distribution of blood vessels, and the time of onset does not match the imaging findings, the possibility of DLGGs should be considered.Abbreviations: ADC = apparent diffusion coefficient, ATRX = alpha thalassemia/mental retardation syndrome X-linked, CE-MRA = contrast-enhanced magnetic resonance angiography, CKP = cytokeratin pan, CT = computed tomography, DLGGs = diffuse low-grade gliomas, DWI = diffusion-weighted imaging, FLAIR = fluid-attenuated inversion recovery, GFAP = glial fibrillary acid protein, IDH = isocitrate dehydrogenase, MGMT = O-6-methylguanine-DNA methyltransferase, MRI = magnetic resonance imaging, NIHSS = National Institute of Health Stroke Scale, rtPA = alteplase, T1WI = T1-weighted imaging, T2WI = T2-weighted imaging, TERT = telomerase reverse transcriptase.