Genetically attenuated malaria parasites with essential gene deletions are potent malaria vaccine candidates. CRISPR/Cas9-based gene editing is now a preferred method to create these parasites by deleting genes that are critical to parasite development. In order to improve the CRISPR/Cas9 system for use in malaria parasites, we have used a GFP-reporter system to define and modulate the Plasmodium yoelii HSP70-2/BiP promoter, to in turn be able to optimize Cas9 transcription and protein expression in vivo.