Embodiments relate to multithreading capability information retrieval. An aspect is a computer system includes a configuration with one or more cores configurable between a single thread (ST) mode and a multithreading (MT) mode. The ST mode addresses a primary thread and the MT mode addresses the primary thread and one or more secondary threads on shared resources of each core. The computer system also includes a multithreading facility configured to control utilization of the configuration to perform a method that includes executing, by the core, a retrieve multithreading capability information instruction. The execution includes obtaining thread identification information that identifies multithreading capability of the configuration, and storing the obtained thread identification information.