Combustion kinetics of (-210+149), (-149+88) and (-88) m particle size Goynuk oil shale was investigated under non-isothermal conditions with a heating rate of 5, 10, and 20 K/min in the 298-1,173 K temperature interval under air atmosphere. The combustion characteristics of the samples were analyzed using thermogravimetric/differential thermogravimetric curves. Differential thermogravimetric data were analyzed by two different models and apparent activation energies of the samples were determined. Minimum activation energy was obtained as 1.8 kJ/mol with 20 K/min in (-88) m.