He is best known for his work on topology, including the metrization theorem he proved in 1926, and the Tychonoff's theorem, which states that every product of arbitrarily many compact topological spaces is again compact.
Han er bedst kendt for sit arbejde inden for topologi; herunder på metriseringssætningen som han beviste i 1926, samt Tikhonovs sætning, der siger, at ethvert produkt af vilkårligt mange kompakte topologiske rum igen er kompakt.