Dynamic stretching (DS) uses a controlled movement through the range of motion (ROM) of the active joint(s) by contracting the agonist muscles without being held in an end position. In contrast, ballistic stretching (BS) typically uses uncontrolled movements of a higher velocity with bouncing actions. However, BS is often considered to be a form of DS. When considered together, DS and BS reportedly increase flexibility, evidenced by single- and multiple-joint ROM improvements and other measurements. However, a meta-analysis with subgroup analyses revealing the acute effects of DS and BS on flexibility in detail, independently of other stretching methods, has yet to be conducted. The purpose of this meta-analysis was to investigate the acute effects of DS and BS on flexibility in healthy participants. The PubMed, Web of Science, and Scopus databases were searched for eligible papers published before September 9, 2024; 17 papers were included in the meta-analysis. The main meta-analysis was performed with a random-effect model, and subgroup analyses were performed to examine the effects of age (young vs. middle-aged and older), sex (male vs. mixed sex), stretching methods (DS vs. BS), stretched muscles (hamstrings vs. plantar flexors vs. multiple muscles), and flexibility outcomes (single-joint ROM vs. straight-leg raise test vs. sit-and-reach test). A small increase in flexibility was found following DS and BS (considered together) (effect size = 0.372, Z = 3.936, 95% confidence interval = 0.187–0.557, p < 0.001, I² = 27%). Subgroup analyses revealed no significant differences between age (p = 0.24), sex (p = 0.76), stretching method (p = 0.83), stretched muscle (p = 0.20), or flexibility outcome (p = 0.34) groups. Our results suggest that DS and BS effectively provide acute, small-magnitude improvements in flexibility that are not significantly affected by individual characteristics, stretching methods, stretched muscles, or flexibility outcomes.