Abstract <p>This research paper explores the dynamics of a cascaded optical klystron with betatron oscillations in free-electron lasers theoretically. By integrating multiple optical klystron stages in sequence, energy extraction efficiency and electron bunching are improved. An analytical treatment has been employed to evaluate spectral properties of the free electron lasers. The results demonstrate that the proposed configuration significantly enhances free-electron laser gain and intensity compared to the conventional single-stage optical klystron setup. The Liénard–Wiechert potentials and generalized Bessel functions have been introduced in the analysis. This study reveals that the cascaded optical klystron configuration serves as a highly effective method for improving gain efficiency and enhancing stability in free-electron lasers, even in the presence of the adverse effects of betatron oscillations.</p>