Context <p>The successful synthesis of MA₂Z₄ (M = Mo, W, Nb; A = Si, Ge; Z = P, As) material has recently attracted the interest of researchers. However, they are usually non-magnetic in nature. Based on this, we investigated the geometrical structures, electronic properties and magnetic properties of pure MoSi₂P₄ monolayers and MoSi₂P₄ monolayers adsorbed 3d transition metal elements by first principles. Our results show that pure MoSi₂P₄ is non-magnetic with a bandgap of 0.60&#xa0;eV. After adsorbing the transition metal, the electronic structure of all the systems is changed, showing semiconducting or semi-metallic properties. Among these systems, Co, Cr, Fe, Mn, Ti, and V adsorption systems produced magnetic moments ranging from 1.09 μB to 4.38 μB, and all the remaining systems were calculated to be n-type doped except for the Co adsorption system, which was p-type doped. We have also calculated the magnetic anisotropy properties of all systems. Among them, the Co system exhibits the largest absolute value of 3.02&#xa0;meV/f.u., which shows perpendicular magnetic anisotropy. Our calculations indicate the potential value of monolayer MoSi₂P₄ in the application of spintronic devices.</p> Computational method <p>This work uses the Vienna ab initio simulation package (VASP) software package based on density-functional theory (DFT) for structural optimization, static calculations, electronic structure and magnetic properties. The data were processed using the VASPKIT software package.</p>