A TiNi eutectic braze alloy in foil form is utilized to diffusion braze a powder metallurgy beta gamma alloy with a nominal composition of TiAl-4Nb-3Mn (at%). The parent material is consolidated by a two-step hot isostatic pressing process, followed by a step-cooled solution heat treatment to produce a fully lamellar microstructure with fine lamellae and limited beta phase growth at the colony boundaries. Diffusion brazing experiments are conducted under vacuum at various isothermal holding temperatures and times ranging from 1030C for 30 minutes to 1150C for 70 minutes. The typical microstructures and mechanical properties of the joints are characterized by SEM, EDS, and microhardness measurements. The interfacial morphology of the brazed joints changes primarily with isothermal holding temperature. Microhardness levels reduced with diffusion brazing at 1150 C for 70 minutes due to reduced volume fraction of nickel rich phases and increased volume fraction of the gamma phase at the centerline of the joint.