One of the main goals of studying semileptonic decays in flavor physics is to gain a better understanding of hadronic transitions in the nonperturbative region of Quantum Chromodynamics. This involves measuring Cabibbo-Kobayashi-Maskawa matrix elements, understanding form factors, and comparing them with theoretical predictions. We report a first study of the semileptonic decay D⁰ → K^-π⁰μ⁺ν_μ by analyzing an e⁺e^- annihilation data sample of 7.93 fb^-1 collected at the center-of-mass energy of 3.773 GeV with the BESIII detector. The absolute branching fraction of D⁰ → K^-π⁰μ⁺ν_μ is measured for the first time, providing necessary input for extracting the c → s Cabibbo-Kobayashi-Maskawa matrix element through this process. This measurement allows us to test lepton flavor universality, with no indication of violation found. Furthermore, a series of hadronic form factors have been determined and compared with theoretical predictions, which will impose stricter constraints on theoretical models.