A detailed investigation carried out by first-principle spin-polarized density functional calculations using linearized augmented plane wave (LAPW) approach for structure, electronic, and magnetic properties of Mn-doped CdGeAs2. Tran-Blaha’s modified Becke- Johnson (TB-mBJ) functional with local density approximation (LDA) is utilized for potential calculations. This analysis covers the structural, electronic, and magnetic properties of Mn doped CdMnxGe(1−x)As2 where, x changes within the range of 0 ≤ x ≤ 0.5. In structural property, stability of the compound within all given concentration ranges was determined, where the stability of the compound decreases with increase in doping concentration. Density of states of the Mn doped compounds are calculated and results, the Mn-doped compound exhibits half-metallic behavior and p-type semiconducting nature. Electronic properties of Mn doped compounds for thw same Mn doping concentrations were studied and observations show an increase band gap in majority spin states with a rate of 0.08 eV per concentration by weight of the dopant, while minority spin states behave as degenerate semiconductor with an effective zero band gap. Furthermore, magnetic properties of the compound were also investigated and we observed that the magnetic moment per atom linearly increases by 0.05 µB per increase in the concentration of the dopant. The large spin moment observed in Mn-doped CdGeAs2 suggests its potential applications in spintronics, magnetically controlled optical switching devices, and flash NAND memory devices.