In this work, a novel sensor based on immobilised copper phthalocyanine, 2,9,16,23-tetracarboxylic acidpolyacrylamide (Cu(II)TC Pc-PAA) was developed for determination of acid phosphatase (ACP) levels in nanomolar quantities. Detection was based on the measurement of enzymatically generated phosphate, with initial studies focused on phosphate detection at a Cu(II)TC Pc-PAA modified screen-printed gold transducer. The sensor was characterised in relation to operational performance (pH, response time, stability, linearity, and sensitivity) and common anionic interferents (nitrate, sulphate, chloride, and perchlorate). The functionalised surface also facilitated rapid detection of the enzyme bi-product 2- naphthol over the range 5e3000 mM. Quantitation of ACP was demonstrated, realising a linear response range of 0.5e20 nM and LOD of 0.5 nM, which is within the clinical range for this prostate cancer biomarker.