In this study, a robust feedforward hybrid active noise control (ANC) system with online secondary‐path modelling (SPM) is proposed that is capable of not only effectively suppressing the broadband and narrowband noise components but also tracking the secondary path (SP) variations. An finite impulse response online SPM subsystem as well as an efficient decoupling filter are included in the proposed feedforward hybrid ANC (HANC) system. The decoupling filter is a parallel‐form bandpass filter bank that consists of multiple bandpass filters that are derived from the second‐order infinite impulse response notch filters. It takes the residual noise as its input and separates the broadband component from the narrowband component, with the former used as not only a desired signal for the SPM but also as an error signal for updating the broadband sub‐controller, whereas the latter adapted simultaneously to scale the auxiliary white Gaussian noise and to update the narrowband sub‐controller. Extensive simulations are conducted with both the synthetic and real SPs as well as the synthetic and real noise signals that are generated by a large‐scale factory cutting machine (strand‐cutter) to demonstrate the advantages and effectiveness of the proposed feedforward HANC system. Comparisons are also demonstrated with the original HANC system as well as its directly extended version with an online SPM subsystem. A robust feedforward HANC with online SPM is proposed by wise use of an efficient decoupling filter that is based on a parallel‐form bandpass filter bank, which significantly reduces the coupling among the two sub‐controllers and the online SPM subsystem. The new system can not only effectively suppress the broadband and narrowband noise components but also track the secondary path variations simultaneously. The proposed system enjoys major advantages of improved SPM accuracy, faster system convergence as well as significantly improved noise reduction performance.