<p>Mangrove productivity and carbon sequestration are sustained by efficient leaf litter decomposition, contributing to environmental balance in adjacent systems. This study evaluated the synergistic interactions among mangrove tree species on decomposition rates and nutrient release patterns in Amazonian mangroves. Experiments were conducted under three distinct environmental conditions: air, floor, and water. The decomposition rate varied among mangrove species and across environmental conditions, with the highest rates observed under water immersion. In contrast, decomposition in air was the slowest, especially for <i>Laguncularia racemosa</i> (white mangrove; k = 0.0051 day^− 1), highlighting the influence of moisture on organic matter breakdown. The half-life (<i>t</i>_0.5) of leaf litter varied across species and conditions, with <i>Avicennia germinans</i> (black mangrove) showing the fastest decomposition under water immersion (<i>t</i>_0.5 = 10.853 days) and <i>L. racemosa</i> (<i>t</i>_0.5 = 115.80 days) the slowest under air exposure, confirming that environmental moisture strongly accelerates decomposition. These results highlight that the dynamics of decomposition and nutrient release differ among mangrove species and environmental conditions. Submerged leaves decomposed more rapidly, particularly in <i>A. germinans</i>, due to greater nitrogen availability, while <i>L. racemosa</i> retained calcium for more extended periods. The mixed treatment showed intermediate behavior, suggesting that species interactions influence decomposition processes in Amazonian mangroves.</p>