Bioactive paper, or paper that exhibits biorecognition properties, is a promising tool for on-site environmental monitoring. A critical parameter for production of paper-based sensors is the immobilization of biomolecules onto paper with retention of long-term activity. High loading, control over biomolecule orientation and accessibility, and protection of biomolecules from external denaturation need to be provided by the immobilization technique. We present here a summary of the current strategies for enzyme, antibody, bacteriophage, and aptamer immobilization on cellulose and provide examples of the application of bioactive paper in environmental monitoring.