<p>This study systematically compared the effects of different activation sites and modes on serve velocity (SV) and serve accuracy (SA) across multiple time windows to clarify the time course and practical significance of post-activation performance enhancement (PAPE). A 3 (activation site: upper limb, lower limb, full body) × 2 (activation mode: ballistic training, BT; high-resistance training, HRT) × 6 (time: PRE, 3, 6, 9, 12, 15&#xa0;min) design was employed. SV was analyzed using repeated-measures ANOVA, and SA, which did not meet normality assumptions, was analyzed with generalized estimating equations (GEE). Percentage changes (Δ%) were calculated for confirmatory analysis. SV showed significant main effects of time (F = 212.33, <i>p</i> &lt; 0.001, η²<i>p</i> = 0.910), activation mode (F = 34.57, <i>p</i> &lt; 0.001, η²<i>p</i> = 0.622), and a Time × Activation mode interaction (F = 7.423, <i>p</i> &lt; 0.001, η²<i>p</i> = 0.261), with BT producing higher SV overall. SVΔ% analysis indicated BT advantage in the early-to-mid window (3–9&#xa0;min), with upper-limb and full-body BT exceeding lower-limb HRT (<i>p</i> &lt; 0.01, Cohen’s d = 2.08–3.77). SA showed a significant time effect (Wald χ² = 222.40, <i>p</i> &lt; 0.001), but no differences were observed between activation conditions at the same time points (all <i>p</i> &gt; 0.05). SV increased after activation, with BT producing greater improvements within 3–9&#xa0;min. Upper-limb and full-body activation tended to outperform lower-limb activation. SA changed over time, without consistent between-condition differences.</p>