By measuring ultrasonic velocity in Li 2 SO 4 -MgO-P 2 O 5 glasses doped with different concentrations of NiO, we have evaluated different elastic coefficients; the values of these coefficients exhibited a decreasing trend with increase of nickel oxide concentration up to 0.8 mol%. This is ascribed to increasing presence of nickel ions in octahedral positions that act as modifiers and are predicted to have induced structural defects like dangling bonds in the glass network. Such increased degree of disorder in the glass network is anticipated to be a hindrance for the propagation of ultrasonic waves and hence caused the decrease in the velocities of ultrasonic waves and elastic coefficients. Overall, there is a decrease in mechanical strength of these glasses with increased content of nickel oxide up to 0.8 mol%.