Mineral scale (scale) is the crystalline inorganic precipitate from aqueous solution. Scale formation in pipelines has long been a challenge in various industrial systems. Micro/nano plastics (MNPs) have the potential to strongly influence scale formation process. However, comprehensive studies and mechanistic understanding of the interactions between MNPs and scales remain significantly underexplored. To fill this gap, we firstly adopted quartz crystal microbalance with dissipation (QCM-D) technology to monitor the in situ formation of barium sulfate (BaSO₄) (0.001 M, saturation index 2.5) scale influenced by MNPs on metal surfaces. Microplastic (MP) (5 µm)-loaded surface exhibits hydrophobicity (contact angle > 123.1º), which reduces the rate of scale formation (90.86 ± 11.01 (ng cm⁻²min⁻¹)). Electrostatic repulsion impeded crystal growth while ion adsorption has a limited effect. Experiments on BaSO₄ formation on metal pipes loaded with foam packaging debris were conducted over 30 days, and similar inhibition results were obtained. This study highlights the important role of MNPs in controlling heterogeneous nucleation and crystal growth of scale on metal surfaces, providing valuable insights for both MNPs and scale research.