<p>Pipelines for fluid conveyance are widely employed across a range of engineering applications, including petrochemical plants, natural gas plants, nuclear power stations, water treatment plants and subsea systems. However, unexpected vibrations from various sources can compromise their operational performance and cause damage to the systems. Among piping systems, the pipe-in-pipe (PIP) system is ubiquitous, offering the benefits of thermal insulation and reduced vibration levels. Thus, this study investigates a non-compliant viscoelastic PIP system subjected to harmonic excitation, focusing on vibration analysis and its control. Modelling employs Euler–Bernoulli beam theory, with the dynamic equations derived using the Galerkin method. Initially, optimal centralizer locations are determined to minimize the system amplitude. A comparison between the use of a linear and Duffing nonlinear centralizers is also studied. A nonlinear energy sink (NES) is then integrated into the system, whose optimal stiffness and damping properties for a given mass are determined using an optimization technique. Additionally, some improvement in the nonlinear responses at higher excitation amplitudes has also occurred for a range of NES parameters. It reduces the first resonant peak of the outer pipe as well as the inner pipe in broader frequency range than linear vibration absorber. It is observed that increasing NES stiffness and mass enhances the unstable band and resonant peaks, while higher damping reduces the unstable band of the steady-state responses. The study concludes that the NES application is promising, particularly for attenuating vibrations in the outer pipe and whole system stability.</p>