Structural studies have been performed on precipitation hardening found in $L1_2$ ordered ${gamma}^{prime}-Ni_3(Al,Ti)$ alloys using transmission electron microscopy. A uniform solid solution of ${gamma}^{prime}-L1_2$ ordered phase supersaturated with Ni can be obtained by solution annealing in a suitable temperature range. The ${gamma}^{prime}$ phase hardens appreciably by the fine precipitation of disordered ${gamma}$. The shape of ${gamma}$ precipitates formed during aging is initially spherical or round-cubic and grow into platelets as aging proceeds. High resolution electron microscopy revealed that the ${gamma}$ precipitates are perfectly coherent with the matrix ${gamma}^{prime}$ as long as the ${gamma}$-precipitates are plates. The loss of coherency initiates by the introduction of dislocations at the ${gamma}/{gamma}^{prime}$ interface followed by the step formation at the dislocations. The ${gamma}$ precipitates become globular after the loss of coherency. The strength of ${gamma}^{prime}-Ni_3(Al,Ti)$ increases over the temperature range of experiment by the precipitation of fine ${gamma}$ particles. The peak temperature where a maximum strength was obtained shifted to higher temperature.