<p>Considerable amounts of engineering construction were performed in cold regions where peat soil deposits exist extensively in the Western Sichuan Plateau, China. However, the mechanical properties of frozen peat soil have rarely been reported. In this paper, a series of unconsolidated undrained direct shear tests were carried out on frozen peat soil at varying freezing temperatures and times. The experimental results indicated that the measured cohesion varies from 16 to 31 kPa, and the friction angle varies from 21.2° to 27.8°, with the freezing temperature varying from 0°C to −25°C and the freezing time varying from 6 to 30 h. The growth rate of cohesion is at a maximum when the freezing temperature decreases to −5°C. Both cohesion and friction angle tend to be relatively stable when the freezing temperature decreases to −25°C. Additionally, when the freezing time is greater than 24 h, the growth rates of cohesion and friction angle tend to be stable. The established relations of the shear strength with freezing temperature and freezing time indicate that freezing time contributes more to the growth of cohesion than freezing temperature. This is because the structures of frozen soil have become increasingly dense due to persistent freezing resulting in stronger cementation between ice and soil particles. In contrast, the freezing temperature contributes more to the growth of the friction angle than the freezing time.</p>