Classical molecular dynamics with the AIREBO potential is used to investigate and compare the thermal conductivity of both zigzag and armchair graphene nanoribbons possessing various densities of Stone–Thrower–Wales (STW) and double vacancy defects, within a temperature range of 100–600 K. Our results indicate that the presence of both kinds of defects can decrease the thermal conductivity by more than 80% as defect densities are increased to 10% coverage, with the decrease at high defect densities being significantly higher in zigzag compared with armchair nanoribbons. Variations of thermal conductivity in armchair nanoribbons were similar for both kinds of defects, whereas double vacancies in the zigzag nanoribbons led to more significant decreases in thermal conductivity than STW defects. The same trends are observed across the entire temperature range tested.