<p>Polycyclic aromatic hydrocarbons (PAHs), as ubiquitous hydrophobic pollutants, pose serious risks to aquatic ecosystems and human health due to their bioaccumulation and toxicity. Polymer-water partition coefficients (<i>K</i>_pw) are crucial for calculating the freely dissolved concentrations of these pollutants in water during passive sampling. This study experimentally determined <i>K</i>_pw values for the novel butyl rubber passive samplers (BR) for the first time and also for the polydimethylsiloxane (PDMS) as a reference passive sampler using the co-solvent method with methanol as co-solvent for 15 PAHs. The determined log <i>K</i>_pw values for PDMS samplers ranged from 3.6 to 6.4, while single-network BR (SN10) and triple-network BR (TN) samplers showed narrower ranges of 3.0 to 4.6 and 3.0 to 3.7, respectively. First- and second-order regression analyses revealed that molecular weights better represent the partitioning behavior of PAHs rather than octanol–water partition coefficients. The second-order regression equations, with correlation coefficients (<i>R</i>²) from 0.83 to 0.98, facilitate the estimation of <i>K</i>_pw values for BR samplers for other organic pollutants and provide validation data for future model studies.</p>