The genus Acanthaspis (Heteroptera: Reduviidae) contains ecologically significant predatory assassin bugs noted for their complex camouflage behaviours and potential as biological control agents. Despite their importance, the evolutionary relationships within this genus remain poorly understood due to limited genomic data and morphological convergence. Mitochondrial ribosomal RNAs (rrnS and rrnL) offer a balance of conserved and variable regions, making them ideal markers for resolving lower-taxonomic relationships. The current study performed a comparative mitochondrial ribosomal RNAs analysis of Acanthaspis pedestris, A. cinctricus and A. ruficeps. Ribosomal RNA sequences were retrieved from RefSeq, aligned using the MAFFT G-INS-i algorithm and analysed for nucleotide composition, strand asymmetry and sequence conservation. Phylogenetic trees were reconstructed using the Neighbor-Joining method with the Jukes–Cantor (JC69) substitution model to evaluate gene-specific evolutionary signals. Both rRNA genes exhibited A+T bias (70.93%–72.26% for rrnS; 73.80%–76.19% for rrnL), negative AT skews and positive GC skews. High conservation rates were observed in rrnS (93.62%) and rrnL (92.68%) showed slightly higher sequence divergence. The phylogenetic reconstruction revealed different branching patterns, rrnS placed A. ruficeps and A. cinctricus as sister taxa, whereas rrnL grouped A. pedestris with A. ruficeps. These findings confirm that while mitochondrial rRNAs are structurally stable in Acanthaspis, they capture distinct evolutionary signals. This difference in branching patterns reveals the limitations of single-gene mitochondrial phylogenetic analysis and highlights the necessity of multi-locus or integrative phylogenetic approaches to resolve the complex systematics of the Reduviinae subfamily. These results provide a foundational framework for future genomic investigations into the diversification of predatory Hemiptera.