The grain boundary character distribution (GBCD) of a fully-orthorhombic (O) Ti–25Al–24Nb (at.%) microstructure was investigated using electron backscatter diffraction (EBSD). The fine-grained (GS=17 μm) equiaxed microstructure was processed by hot forging and hot-rolling operations performed below the body-centered cubic (bcc) phase transus temperature followed by heat treatment in the O-phase field at 875 °C. Nearly all the O/O grain boundaries were greater than 15 degrees misoriented and such boundaries exhibited the highest frequencies at misorientations of approximately 65° (∼26% of all grain boundaries) and 90° (∼10% of all grain boundaries). Twin-related O-phase variant interfacial (1 1 0) planes were identified and such boundaries represented 39% of all the O/O grain boundaries with 65° misorientation about [0 0 1].