The Cassidinae family, comprising unique and beautiful leaf beetles, has been the subject of limited research regarding its diversity and richness in Malaysia. Consequently, this study aimed to perform DNA barcoding on the Cassidinae species collected from Peninsular Malaysia by using the cytochrome c oxidase subunit I (COI) gene. Prior to molecular work, each species was identified morphologically based on external morphological characteristics. This study reconfirmed the host plant record for only one species, Silana farinosa, which infests the curry leaf, Murraya koenigii. Notably, a total of ten species were morphologically identified, including those belonging to the tribe Aspidimorphini (Aspidimorpha assimilis, Aspidimorpha elevata, Aspidimorpha malaccana, Aspidimorpha miliaris, and Laccoptera nepalensis) and tribe Cassidini (Chiridopsis punctata, Cassida circumdata, Chiridopsis scalaris, Notosacantha taeniata, and Silana farinosa). In this study, only seven species were successfully barcoded, and the resulting data have been deposited in GenBank. Remarkably, the separation of species is clearly delineated within their respective lineages on the Neighbor-Joining tree, with the exception of several species that predominantly belong to the genus Aspidimorpha. The data gathered in this study are significant and contribute valuable information for genetic conservation and the preservation of plant species.