Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive motor neuron (MN) loss. The most common genetic cause, a hexanucleotide repeat expansion in C9orf72 (C9-ALS), disrupts microglial function, contributing to neuroinflammation, a key disease driver. To investigate this, we developed a three-dimensional spinal microtissue (SM) model incorporating human induced pluripotent stem cell (hiPSC)-derived MNs, astrocytes, and microglia. Screening 190 Food and Drug Administration (FDA)-approved compounds, we identified sartans-angiotensin II receptor I blockers (ARBs)-as potent inhibitors of neuroinflammation. Telmisartan, a highly brain-penetrant ARB, significantly reduced the levels of pro-inflammatory cytokines interleukin (IL)-6 and IL-8 and rescued MN loss in C9-ALS SMs. Our findings suggest that C9-ALS microglia drive MN toxicity and that telmisartan can effectively mitigate inflammation and preserve MN viability. This work lays the groundwork for modeling disease-related neuroinflammation and points to telmisartan as a therapeutic candidate worth further exploration for treating C9-ALS.