The effect of methyl jasmonate (MeJA) on frost resistance, photosynthetic and respiratory activity, and water metabolism in wheat plants (Triticum aestivum L.) exposed to a low hardening temperature (4 °С) was studied. It was found that under hardening conditions, treatment with MeJA led to a greater increase in the plants’ frost resistance than without it, and also augmented dry shoot and root biomass gain. In addition, pretreatment with MeJA helped the seedlings maintain a higher rate of net photosynthesis and transpiration, and increased stomatal conductance during the hardening period. Also, the rate of dark respiration was observed to rise in the presence of MeJA, leading an increase in the ratio of respiration to gross photosynthesis (Rd/Pg). Based on the obtained results, it was concluded that MeJA had a positive effect on the cold adaptation of wheat plants, which is due to its regulatory effect on the main physiological processes.