Based on the density-functional theory, geometric, energetic, electronic, and magnetic properties of phosphorus-doped small titanium clusters TinP (n=1–12) have been investigated. For the ground state structures of Ti10P, Ti11P, and Ti12P clusters, the P atom completely fell into the center of the clusters forming the P-encapsulating Ti cage clusters. Doping of the P atom enhanced the stability of the Ti clusters. The binding energies, second-order energy differences, and fragmentation energies with the size of clusters showed Ti6P and Ti12P to be endowed with special stability. The total magnetic moments of TinP clusters exhibited odd–even staggering behavior. The quenching of the magnetic moment has not been found in TinP clusters. The density of states of clusters was discussed to understand the origin of peculiar magnetic properties.