The blattid cockroach Periplaneta arabica (Bey-Bienko, 1938) has been poorly understood since its original description. In this study, male and female (including nymph) of P. arabica are paired using DNA barcoding, and their morphological characters (including both external characteristics and genitalia) are described. A detailed comparative morphological study of this species and the closely related Periplaneta americana (Linnaeus, 1758) and Periplaneta lateralis Walker, 1868 was carried out to explore phylogenetically relevant characters.