Organic electrochemical transistors (OECTs) are increasingly studied for sensing applications. While analyzing and maximizing OECT signal has been emphasized, noise has been mostly ignored, even though it limits a sensor's resolution. The authors demonstrate that $1/f$ noise in OECTs is due to charge fluctuations near or within the channel material. The magnitude of this noise is similar to that observed in graphene transistors, and only slightly higher than in devices based on carbon nanotubes or silicon nanowires. For best results, design large-area channels.