We report the results of the Y substitution in Sr 1−x Y x Si 2 with x Յ 0.15 via measuring the temperature-dependent electrical resistivity, thermal conductivity, as well as Seebeck coefficient. Upon substituting Y onto the Sr sites, the electrical resistivity exhibit semiconducting behavior and the room-temperature electrical resistivity tends to reduce for x Յ 0.08. The thermal conductivity also decreases with increasing the Y content. Moreover, the Seebeck coefficient has a substantial increase and a maximum of about 220 V / K at around 80 K has been found for x = 0.08. These promising effects lead to a significant enhancement in the thermoelectric performance characterized by the figure-of-merit, ZT. A room-temperature ZT value of approximately 0.4 is thus achieved for Sr 0.92 Y 0.08 Si 2 , about one order of magnitude larger than that of stoichiometric SrSi 2 .