Study Objective: This study investigated the effects of chronic ankle instability (CAI) on axial (neck and trunk) and lower-extremity joint kinematics during a side cutting jump to identify compensatory strategies across the kinetic chain. Methods: Twenty-seven male adults in their 20s participated, including fourteen with CAI and thirteen healthy controls. CAI was defined as a Cumberland Ankle Instability Tool-Korean version (CAIT-K) score ≤ 24 and an Identification of Functional Ankle Instability-Korean version (IdFAI-K) score ≥ 11. Participants performed side cutting jumps on a force plate while three-dimensional joint kinematics were captured using a 14-camera motion system (100 Hz). Eighteen joint angles from the upper body to the ankle were analyzed. Group differences across the movement phase (initial contact to 1 s post-landing) were assessed using Statistical Parametric Mapping (SPM1D) with Bonferroni correction (α = 0.00085). Results: Compared with controls, the CAI group showed smaller neck motions across all planes, which may suggest a potential reliance on visual stabilization. Trunk flexion and rotation were greater, which is consistent with a potential mechanism for impact absorption. At the pelvis and hip, CAI participants displayed increased anterior tilt, greater flexion and internal rotation, and reduced abduction. Notably, at the knee, flexion was significantly greater during the 1.7–32.8% phase (peak d = 1.06, large effect size) with smaller valgus and rotational angles. At the distal level, the ankle showed a significant increase in eversion during the 3.4–15.5% phase (d = 0.00–0.28) and external rotation during the 5.2–13.8% phase (d = 0.28–0.48), representing a compensatory pronation-bias strategy. Conclusions: CAI alters not only ankle function but also global coordination during side cutting jumps, reflecting multi-joint compensatory mechanisms to stabilize posture and modulate kinematic forces. Compensatory strategies involving visual fixation, trunk modulation, and proximal joint adjustments highlight the need for an integrated kinetic chain approach in CAI evaluation and rehabilitation.