Single crystals of (Mo0.8Nb0.2)(5)Si-3, (Mo0.85W0.15)(5)Si-3 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 (alpha(c)/alpha(a)) is lower for (Mo0.8Nb0.2)(5)Si-3, and higher for (Mo0.85W0.15)(5)Si-3 at RT than that for Mo5Si3. However, the alpha(c)/alpha(a) for (Mo0.8Nb0.2)(5)Si-3 increases with increasing temperature and the alpha(c)/alpha(a) of the three compounds is similar at 800 degrees C. The values of isotropic average Young's (E), bulk (K) and shear (G) moduli for (Mo0.8Nb0.2)(5)Si-3 is the lowest and those for (Mo0.85W0.15)(5)Si-3 is the highest in the three compounds. On the other hand, the difference of E between [100] and [001] 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.