The Ca2+ release-activated Ca2+ (CRAC) channels control many Ca2+-modulated physiological processes in mammals. Hyper- activating CRAC channels are known to cause several human diseases, including Stormorken syndrome. Here, we show the design of azopyrazole-derived photoswitchable CRAC channel inhibitors (designated piCRACs), which enable optical inhibition of store-operated Ca2+ influx and downstream signaling. Moreover, piCRAC-1 has been applied in vivo to alleviate thrombocytopenia and hemorrhage in a zebrafish model of Stormorken syndrome in a light-dependent manner.