The effects of metallization thickness on the thermal and long‐term stability of Pd/Sn Ohmic contacts have been investigated. Metallization samples are furnace annealed at various temperatures and systematically characterized utilizing Scanning Electron Microscopy (SEM) and current–voltage (I–V) measurements. Contact resistivities, ρc, of the metallizations are measured using a conventional Transmission Line Model (cTLM) method. SEM is utilized to investigate the surface morphology of the contacts. Thermal stability analysis of the metallizations is carried out at 410 °C for 10 h, whereas long‐term stability tests are performed at 300 °C for 400 h. After annealing at 410 °C for 10 h, ρc of the Pd(30 nm)/Sn(150 nm) metallization remains in the high 10—5 Ω cm2(90 nm) and Pd(40 nm)/Sn(120 nm) contacts ρc values increase to the mid 10—4 Ω cm2(90 nm) and Pd(40 nm)/Sn(120 nm) contacts. The effects of a highly conductive overlayer, Au, on the thermal and long‐term stability of Pd/Sn Ohmic contacts are also investigated.