A flash output control photography failure warning device in a camera is provided with a quantity-of-light detecting circuit adapted to start operating in synchronism with shutter release and to change from a first condition to a second condition when the integrated amount of the light from an object reaches a predetermined value, a time counting circuit for counting a predetermined time T.sub.2 greater than the longest light emission time of a flashlight discharge tube in synchronism with shutter release, a memory circuit adapted to start memorizing the condition of the quantity-of-light detecting circuit after the longest light emission time of the flashlight discharge tube and before the predetermined time T.sub.2 and to memorize it till a predetermined time T.sub.3, a discrimination circuit for discriminating that the condition of the quantity-of-light detecting circuit memorized by the memory circuit at a point of time whereat the time counting circuit has counted the predetermined time T.sub.2 is the first condition and putting out a failure signal, and warning means controlled by the failure signal of the discrimination circuit.