Abstract. – Mussels are capable of producing byssal threads and plaques to attach onto various surfaces securely in order to adapt to their harsh habitats. This study aims (1) to compare the morphology of byssal threads and plaques of relatively small lesser-known mussels, Xenostrobus mangle with larger mussels, Perna viridis using light microscopy and (2) to identify the attachment ability of X. mangle on different substrates. Results showed that the byssal threads of X. mangle are thin (0.07 ± 0.02 mm proximally and 0.08 ± 0.02 distally in diameter) and structurally appear to be less fibrous whilst the byssal threads of P. viridis are relatively thicker (0.18 ± 0.01 mm proximally and 0.20 ± 0.01 mm distally in diameter) and fibrous. Intriguingly, the average lengths of byssal threads for both mussels are approximately one third of their shell lengths in spite of their differences in size. The attachment plaques for both X. mangle and P. viridis are uneven in appearance and the attachment plaques of X. mangle are smaller than that of P. viridis. Surface attachment ability test for X. mangle has revealed that the mussels can adhere onto nine different substrate surfaces (wood, rock, silica glass, rubber latex, ceramic, stainless steel, nylon, polystyrene, polyvinylchloride) using their byssi.