Stroke contributes to disability in adulthood. The assessment of the degree of spasticity is one of the basic methods of patient examination after stroke and is used for monitoring rehabilitative outcomes; however, no optimal scale for the unambiguous assessment of spasticity exists. Our study aimed to assess the usefulness of thermography in measuring the effects of rehabilitation in stroke patients' spastic hemiparesis. In this prospective, single-center study, 40 stroke patients with a mean age of 60.6 ± 5.5 years were enrolled. All suffered from hemiparesis. Surface temperature of the shank was assessed with infrared thermography; degree of independence with the Barthel Index; and muscle tone with the Modified Ashworth Scale. A comparison of temperature between the spastic and non-spastic posterior part of the shank was conducted. Temperature changes, severity of spasticity, and gait pattern were evaluated and compared at baseline and after 6 weeks of rehabilitation. All patients completed a rehabilitation program. The baseline temperature in the spastic extremity was significantly lower than in the normal extremity (mean temperature 28.93°C vs 30.20°C; p = 0.0001). After rehabilitation, the temperature in the spastic extremity increased significantly; however, the significant difference between the two extremities persisted (mean temperature 29.76°C vs 30.54°C; p = 0.0001). After rehabilitation, spasticity in affected extremity decreased significantly (p [ 0.001). Additionally, an improvement in gait pattern was observed. We conclude that thermography proved to be useful in the assessment of rehabilitation effects in stroke patients with spastic hemiparesis; thus, it can be considered an additional tool for determining impaired muscle tone in patients with spasticity.