Dissolved element concentrations, dissolved stable carbon isotope ratios (δ13C), salinity measurements, and suspended particulate matter (SPM) concentrations from the Mackenzie River and estuary. River water and SPM samples were collected between the 11th and the 18th of September 2022. Samples were taken from the surface of the water column and at depth. Individual sample locations (latitude and longitude) are provided in the data file. In total, 18 water and SPM samples were collected from 11 different localities. Samples were collected to span a large salinity range (0.15-29 P.S.U.). Dissolved element concentrations provided: aluminium, barium, calcium, iron, potassium, magnesium, manganese, sodium, sulphate, silicon, and strontium.