Handgrip strength (HGS) is a key indicator of muscular fitness and physical health. Recently, attention has focused on HGS asymmetry as a potential marker of functional impairment. The aim of the study was to analyze differences in handgrip strength between the dominant and non-dominant limbs and to assess the influence of age and sex on asymmetry levels within the Polish population. A total of 341 participants (170 women and 171 men) were divided into two groups: younger (18–35 years) and older (50+). HGS was measured using a Noraxon digital dynamometer, and asymmetry was defined as the ratio of dominant to non-dominant handgrip strength. Most of the participants (approximately 70%) exhibited greater strength in their dominant hand, with a mean asymmetry values ranging from 17% to 19%. Older adults showed lower overall HGS than younger adults, however, the asymmetry did not differ significantly between sexes or age groups. A small asymmetry (≤10%) was the most common among participants. The Polish adult population shows moderate asymmetry in handgrip strength, with a predominance of the dominant hand, regardless of age or gender. Measuring grip strength asymmetry may provide useful information for assessing the function of the upper limbs and could be important for monitoring physical fitness, identifying neuromuscular disorders, and preventing the decline of motor function in older adults.