Gold nanoclusters (AuNCs) protected by bovine serum albumin (BSA) can emit red photoluminescence under illumination by ultraviolet light. The luminescence of the BSA–AuNCs was quenched when Cu²⁺ chelated with glycine in the BSA chain and generated BSA–AuNCs–Cu²⁺, while the luminescence of the BSA–AuNCs restored when pyrophosphate ion (P₂O₇⁴⁻, PPi) was added and chelated with Cu²⁺, resulting in Cu²⁺ being removed from the surface of BSA–AuNCs. Bearing this in mind, herein we present a novel BSA–AuNCs–Cu²⁺ fluorescent sensor for PPi detection. This environmentally-friendly, simple, rapid and selective fluorescent sensor possesses a wide linear range (0.16–78.1 μM) and a high sensitivity (the limit of detection (LD) is 0.083 μM), which could also determine PPi in the effluent of copper plating with the results consistent with those obtained by absorptiometry. Furthermore, the morphologies of BSA–AuNCs, BSA–AuNCs–Cu²⁺ and BSA–AuNCs–Cu²⁺-PPi were characterized by high resolution transmission electron microscopy (HRTEM). The mechanism of the proposed assay for PPi detection has been discussed.