In this study, a newly developed near α titanium alloy with a typical Widmannstätten as-cast microstructure was subjected to isothermal multidirectional forging (IMDF) at 15 °C below β transus temperature. Microstructural observations reveal that the prior β grain boundaries disappeared and α laths transformed into spheroids gradually with increasing the IMDF pass. Ultrafine α grains with an average grain size of 1.57 μm was achieved after four-pass IMDF. Microstructural homogeneity was enhanced and the fraction of recrystallized grains increased remarkably with increasing IMDF pass. The spheroidization process of α laths is a result of the recrystallization during IMDF, including the dissociation of α laths and the migration of subgrains. Compared to the as-cast titanium alloy, both the tensile strength and elongation to failure at room temperature were improved, which is primarily attributed to the microstructure refinement and spheroidization of α laths. In addition to grain refinement, dislocation hardening and substructure strengthening are also the critical mechanisms for the increased strength observed in the samples after IMDF.