Artificial radioisotopes of tellurium are known, with atomic masses that range from 104 to 142, of which the most stable is ¹²¹Te with a half-life of 19.31 days. Several nuclear isomers have longer half-lives, the longest being ^121mTe with a half-life of 164.7 days.

The very long-lived radioisotopes ¹²⁸Te and ¹³⁰Te are the two most common isotopes of tellurium. Of elements with at least one stable isotope, only indium