We report first-principles investigation on structural, electronic and magnetic properties of 3d transition metal element-doped rock-salt calcium selenide Ca[Formula: see text]TMxSe (TM = V, Cr and Mn) at concentrations [Formula: see text] = 0.0625, 0.125 and 0.25. We performed the calculations in the framework of the density functional theory (DFT) using the full-potential linearized augmented plane waves plus local orbitals (FP-LAPW+lo) method within the Wu–Cohen generalized gradient approximation (WC-GGA) for the structural optimization and the Tran–Blaha modified Becke–Johnson (TBmBJ) potential for the electronic and the magnetic properties. The computed spin-polarized band structures and densities of states show that Ca[Formula: see text]CrxSe compounds at all studied concentrations are half-metallic ferromagnets with a complete spin polarization of 100% at Fermi-level while the Ca[Formula: see text]VxSe and Ca[Formula: see text]MnxSe are ferromagnetic semiconductors. The total magnetic moments for Ca[Formula: see text]VxSe, Ca[Formula: see text]CrxSe, and Ca[Formula: see text]MnxSe show the integer values of 3[Formula: see text][Formula: see text], 4[Formula: see text][Formula: see text], and 5[Formula: see text][Formula: see text], respectively, with a major contribution of transition metal elements (TM) in the total magnetization. Also, we reported the calculated exchange constants [Formula: see text] and [Formula: see text] and the band edge spin splitting of the valence ([Formula: see text]) and conduction ([Formula: see text]) bands. The ferromagnetism of these compounds is due to the super-exchange and the double-exchange mechanisms in addition to the strong p–d exchange interaction. Therefore, the predicted results indicate that the diluted Ca[Formula: see text]TMxSe (TM = V, Cr, Mn) compounds are suitable candidates for a possible application in the field of spintronic technology.