Single crystals of (Mo0.8Nb0.2)5Si3, (Mo0.85W0.15)5Si3 and Mo5Si3 were grown and their thermal expansion along the a- and c-axes and single crystalline elastic property were investigated. An anisotropy ratio of coefficient of thermal expansion (ac/aa) is lower for (Mo0.8Nb0.2)5Si3, and higher for (Mo0.85W0.15)5Si3 at RT than that for Mo5Si3. However, the ac/aa for (Mo0.8Nb0.2)5Si3 increases with increasing temperature and the ac/aa of the three compounds is similar at 800°C. The values of isotropic average Young’s (E), bulk (K) and shear (G) moduli for (Mo0.8Nb0.2)5Si3 is the lowest and those for (Mo0.85W0.15)5Si3 is the highest in the three compounds. On the other hand, the difference of E between  and  increases when partial substitution of Mo by Nb occurs and it decreases when partial substitution of Mo by W occurs. Simply compared with the results of thermal expansion anisotropy, the result shows opposite tendency.