The effects of mixing sequence of the polyether polyol and curing agent (triethylenetetramine) on mechanical and thermal properties and morphology of epoxy/polyether polyol/organoclay ternary nanocomposites are investigated in this study. The polyether polyol domain size data are relatively unchanged with mixing order both in epoxy/polyether polyol blends and in ternary nanocomposites. Generally, impact strength data of the ternary nanocomposites prepared by the second addition order are higher than the ones produced by the first addition order. Flexural strength and strain at break may be accepted as unaltered generally for the ternary nanocomposites with respect to addition order. Except for the sample containing 3 wt-% Cloisite(R) 30B and 3 wt. % polyether polyol, flexural modulus data are close to each other in ternary nanocomposites. The highest flexural modulus is obtained for the 5 wt-% Cloisite(R) 30B and 3 wt-% polyether polyol sample prepared by the second addition order, as 2978 +/- 27 MPa.