In geotechnical engineering, using additives to improve soils is very important. This research aims to investigate the effects of Temperature and nano-magnetite on the physical and mechanical properties of clayey soil. The selected percentages for nano-magnetite as 0. 0.5, 1, 1.5, and 2% in standard curing conditions (1, 28, and 90 days) and under different temperatures (3 days at 20, 40, and 60oC) to evaluate the physical and mechanical characteristics of the samples, atterberg limits, standard compaction, unconfined compressive strength (UCS), direct shear test (DST), and ultrasonic pulse velocity (UPV) were used. The results of this research show that by adding 1% of nano-magnetite to clayey soil at a temperature of 60oC, the UCS of clayey soil increased by about 175%, and further, according to the DST, it can be seen that the parameters of cohesion and Internal friction angle have increased by 115% and 77% respectively. Also, the UPV was the highest due to the addition of 1% nano-magnetite, which can confirm the results obtained for mechanical tests.