Major Innate Disordered Notch2-Associated Receptor 1 (MINAR1) is known to suppress angiogenesis and breast cancer cell growth and is associated with neurological disorders such as epilepsy. However, its neurobiological function remains unclear. Herein, we reveal the specific expression of MINAR1 in somatostatin (SST)- and parvalbumin (PV)-positive interneurons in the mouse forebrain. To explore its functional significance, MINAR1 conditional knockout (CKO) mice were generated from Nestin-Cre mice. During postnatal growth, gross brain morphology and cytoarchitecture were comparable between MINAR1 CKO mice and littermate controls; adult CKO mice exhibited increased vulnerability to pentylenetetrazole (PTZ)-induced seizures, and this phenotype was also present in SST-Cre-mediated CKO mice. Mechanistically, MINAR1 deficiency selectively impaired SST+ (but not PV+) interneuron excitability, reducing the inhibitory drive toward pyramidal neurons. This defect correlated with decreased G protein alpha S (G alpha s) levels and disrupted G alpha s-cAMP signaling. Notably, pharmacological activation of adenylate cyclase with forskolin rescued this inhibitory defect. Collectively, our results establish MINAR1 as a key regulator of seizure susceptibility, likely via G alpha s-cAMP-dependent modulation of SST+ interneurons, offering a molecular framework for developing targeted epilepsy therapies.