This systematic review and meta-analysis aimed to provide a comprehensive overview of the impact of age-related changes in the mechanical properties of ankle plantarflexor muscles on gait biomechanics and energetics. A systematic search was conducted across three databases (PubMed, Epistemonikos, and Scopus) to identify studies evaluating the mechanical properties of the ankle plantarflexor muscles in relation to gait parameters. Included studies were cross-sectional in design and compared at least two age groups, with one group aged 60 years. Eleven studies met the inclusion criteria. The meta-analysis revealed that aging is associated with a significant decline in ankle plantarflexor strength (Effect Size (ES) = 1.06 [0.55, 1.58];​ p < 0.001), stiffness of the plantarflexor muscles and Achilles tendon (AT) (ES = 0.76;​ 95 % CI = [0.24 1.27];​ p = 0.004), and muscle volume/thickness (ES = 1.37 [0.63, 2.11];​ p < 0.001). The age-related decline in plantarflexor strength was associated with decreased walking speed and ankle power generation, as well as reduced stability and increased energy cost. Lower AT stiffness in older adults was linked to reduced gait economy, while decreased muscle stiffness was associated with shorter step length and lower maximal gait speed. Similarly, age-related reduction in muscle volume/thickness was associated with decreased step length and peak ankle joint torque. This systematic review and meta-analysis highlights that aging significantly alters the mechanical properties of the plantarflexor muscles, strongly impacting gait performance, stability and economy.