The effects of carrier doping on magnetic and electronic properties of two-dimensional (2D) Janus TiXO (X = S, Se) systems are investigated by first-principles calculations. It is found the electronic instability of systems is related with the flat conduction-band edge and high density of states near Fermi energy. At a concentration of electron doping n ranging from ∼10 13 to ∼10 14 cm −2 , the system maintains in a fully spin-polarized state and the Curie temperature ( T C ) is estimated to be above room temperature; while the nonmagnetic semiconductor TiXO monolayer could become a magnetic half-metal when n is varied. The doping-induced magnetisms and T C could be modulated substantially by applying strains and alternating the number of monolayers in Janus TiXO multilayers. The results indicate that the Janus TiXO possesses tunable magnetic properties, providing promising 2D materials for electronics and spintronics applications. • The Janus TiXO (X = S, Se) monolayers are explored by first-principles calculations. • The 2D monolayers and bilayers exhibit ferromagnetic properties. • The magnetic properties can be modulated by electron doping and applied strains.