Abstract
This paper investigates the Hyers–Ulam stability of a class of generalized biquadratic functional equations involving four unknown mappings in non‐Archimedean normed spaces. We analyze a coupled system that simultaneously incorporates additive, quadratic, additive–quadratic, and quadratic–additive behaviors, thereby capturing both symmetric and asymmetric interactions among the variables. By exploiting the ultrametric structure inherent in non‐Archimedean normed spaces, we establish the existence and uniqueness of approximating solutions, together with stability bounds. Furthermore, a known stability result for biquadratic functional equations is recovered as a corollary of the main theorem.