The circadian clock is an innate timing mechanism that regulates behavior and physiology of most organisms. It anticipates fluctuations in daily environmental conditions and synchronizes biological activities accordingly to maximize ecological fitness. Light is its major environmental entraining cue, but temperature also plays a prominent role. Mutations affecting clock control helped understanding clock mechanisms and their neurobiological and genetic backgrounds. The objective of this study is to investigate the effect of the yellow white (y w) mutation in Drosophila melanogaster fruit flies on the circadian regulation of locomotor activity under different temperature conditions. This mutation causes impaired melanisation, eye pigmentation loss, disturbed neurotransmitter distributions and levels, plus some behavioral alterations. These changes are expected to affect circadian regulation. Results revealed that y w mutant flies retained a functional circadian clock, although with some loss of robustness and plasticity to temperature fluctuations. Total daytime and the lights-on activity was higher in y w mutants under high temperature and lower than wildtype CS under lower temperature, while nighttime activity was always lower and lights-off activity was lower at lower temperature. Most importantly, y w mutant flies didn't shift their morning and evening activity peaks sufficiently away from the light phase, in addition to having shorter siesta at all temperatures tested, compared to wildtype. In conclusion, the     y w mutation seemed to disturb circadian control on locomotor activity, which exposes y w flies to higher levels of environmental risk by being active for longer time under high temperature usually correlated with light phase.