The leaching behavior of cesium -134 (Cs-134) from cement mixed with 5%, 11% and 18% of biochar has been investigated accordance with the ANSI/ANS 16.1-2003 method. The leachate was collected and measured using gamma spectrometry after the leaching periods of 2 h, 7 h, 24 h, 14 days, 28 days, 43 days and 90 days. In order to evaluate the leaching behavior of Cs-134 from cement biochar matrix, the cumulative leach fraction, leaching rate, diffusion coefficient and leachability index for Cs-134 were calculated. The compressive strength of the specimen after 90 days of leaching test was also performed to evaluate its durability in the water. The results indicated that the addition of biochar affects the leaching behavior of Cs-134 from the cement matrix. The optimum amount of biochar required to obtain the lowest leachability and the highest compressive strength of Cs-134 was found to be at 11%. The leaching of Cs-134 from cement-biochar matrix was found less than 20%, in which the leaching behavior approximates that of a semi-infinite medium. The leachabilty indices of all specimens were above the recommend minimum value of 6, which suggest the leaching behavior of Cs-134 from cement-biochar matrix occurred in a very slow diffusion.