An apparatus and method for processing non-maskable interrupt source information. For example, one embodiment of a processor comprises: a plurality of cores comprising execution circuitry to execute instructions and process data; local interrupt circuitry comprising a plurality of registers to store interrupt-related data including non-maskable interrupt (NMI) data related to a first NMI; and non-maskable interrupt (NMI) processing mode selection circuitry, responsive to a request, to select between at least two NMI processing modes to process the first NMI including: a first NMI processing mode in which the plurality of registers are to store first data related to a first NMI, wherein no NMI source information related to a source of the NMI is included in the first data, and a second NMI processing mode in which the plurality of registers are to store both the first data related to the first NMI and second data comprising NMI source information indicating the NMI source.