Taking cue from the increase in the superconducting transition temperature (T c ) of Fe 1+x Se via nominal (2wt%) substitution of Cr instead of excess Fe, we have now extended our study with nominal substitution (≤5wt%) with other transition metals (Ni, Co, Fe, Mn, Cr, V and Ti) in place of excess iron. The T c is found to increase (maximum ~11K) or get suppressed depending on the substituted transition metal. Our studies indicate that the superconducting transition temperature depends on ionic size of the transition metal and amount of hexagonal phase present as impurity.