Hexagonal boron nitride (h-BN) and hexagonal boron nitride-titanium diboride (h-BN-TiB2) composites are advanced materials for high-tech applications. They were investigated against gamma radioisotope sources Cs-137 and Co-60 which have gamma peaks 0.662 MeV for Cs-137, and 1.17 and 1.33 MeV for Co-60. Materials have been produced at 1800 C temperature in argon atmosphere without pressure during 2 h time. Linear and mass attenuation coefficients were calculated for the materials. Gamma transmission technique was used in the experiments. The experimental investigated mass attenuation coefficients of the materials for Cs-137 and Co-60 gamma radioisotope sources were compared with XCOM computer code. For h-BN-TiB2 composites the ratio of TiB2 in the composites is 55% by weight. So gamma attenuation effects of adding TiB2 to h-BN were discussed. It could be said that adding TiB2 to h-BN increases the linear gamma attenuation of the samples.