It is still under debate if and how the ‘plastisphere', a plastic-specific microbial community, can emerge and which the underlying processes are. The initial conditioning film of adsorbed dissolved organic matter (DOM) is thought to play a key role for microbial pioneer attachment and subsequent early biofilm formation. In this study, we tested the hypothesis that DOM sorbs selectively to substrates that display different surface properties. Further, we tested whether subsequent early microbial attachment is governed in a substrate-dependent manner. We investigated the adsorption behavior of DOM to polyethylene terephthalate (PET), polystyrene (PS), and glass as a reference material. The organic matter (OM) composition was characterized by Fourier-transform ion cyclotron mass spectrometry and compared to the DOM in the original incubation water. Only a fraction of the original DOM adsorbed to the substrates. We identified major differences in the molecular OM composition between the substrates which were additionally modified by a weathering treatment. The biofilm community was investigated after 24 h and 72 h of incubation by 16S and 18S rRNA gene amplicon sequencing. Early biofilm communities showed a clear time-dependency, however, we could identify a minimal but detectable substrate-specificity for biofilm attachment after 24 h. Conclusively, the adsorbed OM layer reflects the materials' surface properties to some extent and passes on these surface properites to the OM-water interface which in turn may govern microbial colonization.