Unsupported MoS2 and bifunctional MoS2-amorphous silica-alumina (ASA) catalysts, active for hydrogenation and hydrocracking reactions, were obtained by in situ thermal decomposition of molybdenum octoate in the presence of a sulfur source at temperatures between 300 and 400 °C. Unsupported MoS2 was formed at temperatures as low as 300 °C with yields higher than 76%. Increasing temperature increased the degree of sulfidation but also increased particle dimensions and, consequently, decreased the MoS2 dispersion. The presence of ASA reduced MoS2 particle dimensions compared to the unsupported MoS2, while the effect on sulfidation degree was dependent on temperature. High temperature (400 °C) was required to achieve high MoS2 yield due to interactions with the support at lower temperatures. The catalytic activity of the unsupported MoS2 showed that, as a result of the opposing effects of temperature on the MoS2 dispersion and MoS2 sulfidation degree, the activity toward hydrogenation of phenanthrene, reporte...