Sodium aluminophosphate glasses having compositions of xAl2O3(1 – x)NaPO3 (x = 0⋅05–0⋅2) were prepared using conventional meltquench technique. Density, glass transition temperature, microhardness (MH), thermal expansion coefficient (TEC) and transmission characteristics were measured as a function of alumina content for different samples. They were found to depend on O/P ratio with pronounced changes taking place for O/P ratio ≥ 3⋅5. Density, glass transition temperature and microhardness were found to increase up to15 mol% of alumina and then they showed a decreasing trend. Thermal expansion coefficient decreased continuously with alumina content. Optical gaps for different glass samples as measured from transmission characteristics were found to be in the range 3⋅13–3⋅51 eV. It initially decreased with alumina content up to15 mol% and then increased. The behaviour was explained on the basis of change in the average aluminum coordination number from six Al(6) to four Al(4) (i.e. Al(OP)6/Al(OP)4 ratio) along with thechanges in polyhedra linkages in the glass network due to change in O/P ratio.