Animals adapt to ever-changing environments by making novel associations of stimuli and altering innately engrained behaviors accordingly. On making and storing such novel associations, animals form memory consisting of several components with different durations. One example is a Drosophila olfactory aversive learning in which the anesthesia-sensitive memory (ASM) and the anesthesia-resistant memory (ARM) are concurrently generated in a single conditioning session. While several studies suggests the distinction between ASM and ARM in neuronal or molecular level, underlying molecular mechanism is still obscure, mainly due to a lack of information on genes specifically act in each memory component. In the present study we identified a novel gene rgk1 as a specific regulator of ARM formation. Rgk1 belongs to a conserved Ras-related small G-protein RGK family whose functions include the regulation of the Ca2+ channel and the neurite remodeling. We isolated rgk1 in a screening for genes expressed in the mushroom body (MB), a cardinal neuronal structure of olfactory associative memory. Subsequent antibody and knockdown studies demonstrated specific requirement of MB-expressing Rgk1 for ARM, and an experiment with rgk1-miRNA localized the rgk1 function in a subset of MB neurons. A genetic interaction suggests rgk1 may act closely with dunce (a gene encoding a phosphodiesterase), raising a possibility Rgk1 regulating ARM through the modulation of the cAMP pathway. Importantly, over-expression of rgk1 led to an enhanced memory that mainly consists of ARM, pointing to an instructive role of Rgk1 in ARM formation. Thus, our findings demonstrate an importance of Rgk1 in understanding molecular mechanisms that determine the duration of memory whereby animals maximize their adaptation to an environment.