Cationized cellulose filters with coating of oxidized carbonized cellulose (OCC) were successfully fabricated. The OCC-coated filter was demonstrated as a combined surface for adsorption of environmental contaminants and their detection on the filter by surface-assisted desorption ionization-mass spectrometry (SALDI-MS). The cellulose filters were cationized by utilizing 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHTAC) and sodium hydroxide. It was shown that the degree of substitution increased with the CHTAC feed. OCC, synthesized by hydrothermal carbonization of cellulose with subsequent oxidation and dialysis, was attached onto the cationized filters by electrostatic interactions. The filters adsorbed the model contaminant methylene blue (MB) from aqueous solution, and the MB could subsequently be detected on the filter surfaces by SALDI-MS as [M](+) adduct. The OCC coating further improved the relative peak intensity of [M](+) with little background interferences. This work indicates great potential for the OCC-coated filters as a combined surface for rapid monitoring of environmental contaminants.