This data release presents cyanotoxin and multiparameter water-quality sonde data collected from July-October 2020, at eleven sites in the Salem River, New Jersey. Data-collection sites included seven flowing and four impounded reaches of the main stem Salem River. Solid Phase Adsorption Toxin Tracking (SPATT) samplers were deployed at 11 sampling locations during the study period and retrieved after 1-15 days. Discrete grab samples also were collected at each sampling location during SPATT deployment and retrieval. Physicochemical measurements were collected in-situ with a multiparameter water-quality sonde when the SPATT samplers were deployed and retrieved and include measurements of water temperature, pH, specific conductance, dissolved oxygen concentration, and turbidity. Because of analytical expenses, discrete cyanotoxin samples were analyzed at only 10 of the 11 discrete sampling locations, and toxin results from these analyses informed selection of only 4 of the 11 SPATT sampling locations for additional analyses. SPATT sampler extracts and discrete-grab samples were analyzed for four cyanotoxins (anatoxin-a, cylindrospermopsin, microcystin, saxitoxin) by enzyme-linked immunosorbent assay (ELISA).