A simple trinitro cobalt complex [Co(3,3'-diamino-N-methylpropanediamine)(NO2)3] was proven to be photoswitchable at room temperature as the Pca21 polymorph with the maximum nitro-to-nitrito conversion reaching ca. 55%. Solid-state IR, UV-vis and XRD indicate that the transformation can be triggered optically in both ways via 470 nm and 570-660 nm LED light, respectively.