A critical tool for studying gene function is the ability to control gene expression in desired temporal and spatial patterns. The bipartite Gal4/UAS system from yeast has become a powerful tool for manipulating gene expression in many model organisms since its discovery. However, this system has not been shown to work in C. elegans. Here, we systematically compare the transcriptional efficacy of three major components of this system- the activation domain, UAS copy number, and DNA-binding domain, all in order to develop an optimized Gal4/UAS system for gene expression in C. elegans. Most importantly, we find that the performance of Gal4 is heavily dependent on temperature and performs poorly at 20°C or below. To combat this, we use evolutionary analysis to identify a well conserved Gal4 from the yeast Saccharomyces kudriavzevii whose optimal growth temperature is 23-24°C. This new Gal4 is stronger, capable of recapitulating endogenous promoter strength, and also displays temperature robustness across the 15-25°C range. Our optimized Gal4/UAS system is capable of driving expression in a variety of tissues; we go on to demonstrate tissue-specific rescue, as well as gain-of-function channelrhodopsin experiments in neurons. All together, this constitutes a fully functioning bipartite gene expression system to increase the rate and rigor of research in C. elegans biology.