In a recent study, a tree-ring oxygen isotope record (1800–2013) was used as a proxy for Amazon River discharge in order to investigate a solar influence on this river. Here we reinterpreted the results from this study by improving the analyses of tree-ring data, and by considering the recommendations made by authors critical of Sun-climate link studies. We found that strong 1915–2018 evidences of a causal sunspot-Amazon link were previously misinterpreted as weak; causation is supported by the persistence of a sunspot-Amazon flow anticorrelation over the ten consecutive sunspot cycles of 1915–2018. We also noticed that the 1915 onset of the Sun-Amazon link could have been associated with changes in the background states of solar forcing and Amazon climate.