Sexually dimorphic female-limited Batesian mimicry is known to be present in butterflies of the genus Papilio. The sex differentiation transcription factor doublsex (dsx) has been shown to act as the mimetic switch in Papilio polytes, and aspects of its expression and function have been studied. However, little is known about doublsex’s function in the mimicry phenotype of a related species, Papilio lowi. In this study, I investigate doublesex’s role in Papilio lowi through RNAi experiments on wing pattern development, antibody staining experiments on developing wings to determine expression localization, and RNAseq analysis of expression across early pupal wing development. I find that an RNAi knockout of doublesex in female wings yields male-type scales in the regions where dsx expression is knocked down. The RNAseq data shows that doublsex expression in development is quite different in Papilio lowi than it is in Papilio polytes. Based on antibody staining, it is evident that doublesex is expressed in nuclei and that this expression occurs in the regions where specific wing patterning manifests. The results of this investigation are significant for understanding how the same gene can lead to similar phenotypes in related species via molecular mechanisms which only share some similarities.