Results of dilatometric studies on UNiGa single crystals with respect to temperature, magnetic field and hydrostatic pressure are presented. Similar to the magnetism and the electrical-transport properties, also the elastic and magnetoelastic properties are strongly anisotropic. The linear thermal expansion coefficient α along the a-axis (α a ) is always positive, whereas α c is negative up to 70 K. Sharp anomalies in both α a and α c are observed at the magnetic phase transitions. The antiferromagnetic ordering at low temperatures is accompanied by a considerable linear spontaneous magnetostriction of different signs along the a- and c-axis. In the analysis and discussion of these results in conjunction with magnetic and other electronic properties, the anisotropic 5f-ligand hybridization and related exchange interactions are considered as principal mechanisms.