Tropical rainforest carbon and water cycles are typically assumed to be tightly connected – defined here as exhibiting strong positive correlations (R) – since plants exchange water for carbon through stomatal openings. However, our analysis of 40 years of estimates of photosynthesis (GPP; carbon uptake) and evapotranspiration (ET; water loss) across the Congo Basin reveals that equatorial rainforests exhibit weakly positive (R<0.3) or negative (R<0) correlations between GPP and ET. This occurs in regions with lower atmospheric demand for water, and is largely driven by different behaviors during the dry seasons. This implies that seasonal controls on GPP and ET diverge in areas where vegetation experiences less water stress. Moreover, the strength of GPP-ET correlations has declined since 1982 within equatorial rainforests, coinciding with increases in atmospheric demand for water (VPD). This increased demand, along with increases in atmospheric CO₂, likely suppresses GPP but still allows for increases in ET while there is enough water to sustain demand. However, deforested regions and degraded or regrowing forests in the northern and southern parts of the Congo Basin show increasing correlations over time. This highlights contrasting impacts of climate versus anthropogenic change on carbon and water dynamics within the Congo Basin.