Improving the high-temperature strength and stiffness of Ti3SiC2 is the task of many investigations. However, methods for high-temperature strengthening have not been established although various ways are applicable to enhance the room-temperature mechanical properties of Ti3SiC2. In this work, we report that significant strengthening was realized at both room and high temperatures by incorporating a small amount of W into Ti3(Si, Al)C2. The onsite temperature for the rapid degradation of stiffness and strength moved more than 150°C upward to over 1200°C. The flexural strength of 5 at.% W-doped Ti3(Si, Al)C2 is 632.9 MPa at RT and 285 MPa at 1200°C, being 176% and 170% of those for baseline material, respectively.