Thermoelectric materials that can be utilized for direct conversion between heat and electricity have drawn worldwide interests for decades. Bismuth telluride (Bi2Te3) is the best thermoelectric material for electronic cooling and power generation using low-temperature waste heat, whose property enhancement has great impact on applications. Mixing SiC nanoparticles into the p-type BiSbTe matrix is effective for its thermoelectric property enhancement; a high dimensionless figure of merit (ZT) value up to 1.33 at 373 K is obtained in Bi0.3Sb1.7Te3 incorporated with only 0.4vol% SiC nanoparticles of 30 nm in diameter. Such ZT enhancement by SiC dispersion is also found in n-type BiTeSe, but only happens below 450 K and then ZT decreases at higher temperatures. It is found that SiC dispersion decreases the carrier concentration in n-type BiTeSe by strongly changing the amounts of charged point defects. The decreased carrier concentration shifts the maximum ZT value to lower temperatures, and limits the high temperature ZT values due to minor carrier excitation. Further self-tuning carrier concentration by Cu/I doping effectively solves this problem and realizes a ZT plateau at 473-573 K. In addition to ZT improvement, the mechanical strength of both p-type BiSbTe and n-type BiTeSe are dramatically enhanced by SiC nano-dispersion, which is advantageous for thermoelectric devices’ manufacturing and application.