Cobalt-based superalloys consume most of the produced cobalt. The temperature stability of these alloys makes them suitable for turbine blades for gas turbines and jet aircraft engines, though nickel-based single crystal alloys surpass them in performance. Cobalt-based alloys are also corrosion and wear-resistant, making them (along with titanium) useful in medical orthopedic implants that do not wear down over time. The development of wear-resistant cobalt alloys started in the first decade of the 20th century with the stellite alloys, containing chromium with varying quantities of tungsten and carbon. Alloys with chromium and tungsten carbides are very hard and wear resistant. Special cobalt-chromium-molybdenum alloys like Vitallium are used for prosthetic parts (hip and knee replacements). Cobalt alloys are also used for dental prosthetics as a useful substitute for nickel, which may be allergenic. Some high speed steels also contain cobalt for increased heat and wear-resistance. The special alloys of aluminium, nickel, cobalt and iron, known as Alnico, and alloy of samarium and cobalt (samarium-cobalt magnet) are used in permanent magnets.[56] It is also alloyed with 95% platinum for jewelry, yielding an alloy suitable for fine casting and is also slightly magnetic.

Several cobalt compounds are used in chemical reactions as oxidation catalysts. Cobalt acetate is used for the conversion of xylene to terephthalic acid, the precursor to the bulk polymer polyethylene terephthalate. Typical catalysts are the cobalt carboxylates (known as cobalt soaps). They are also used in paints, varnishes, and inks as “drying agents” through the oxidation of drying oils. The same carboxylates are used to improve the adhesion between steel and rubber in steel-belted radial tires. Cobalt-based catalysts are used in reactions involving carbon monoxide. Steam reforming, useful in hydrogen production, uses cobalt oxide-base catalysts. Cobalt is also a catalyst in the Fischer–Tropsch process for the hydrogenation of carbon monoxide into liquid fuels. Hydroformylation of alkenes often uses cobalt octacarbonyl as a catalyst, although it is often replaced by more efficient iridium- and rhodium-based catalysts, e.g. the Cativa process. The hydrodesulfurization of petroleum uses a catalyst derived from cobalt and molybdenum. This process helps to clean petroleum of sulfur impurities that interfere with the refining of liquid fuels.

Cobalt-60 (Co-60 or 60Co) is useful as a gamma ray source because it can be produced in predictable quantity and high activity by bombarding cobalt with neutrons. It produces two gamma rays with energies of 1.17 and 1.33 MeV.

It is used in external beam radiotherapy, sterilization of medical supplies and medical waste, radiation treatment of foods for sterilization (cold pasteurization),[69] industrial radiography (e.g. weld integrity radiographs), density measurements (e.g. concrete density measurements), and tank fill height switches. 

Cobalt is used in electroplating for its attractive appearance, hardness, resistance to oxidation; it is used as a base primer coat for porcelain enamels.