<p>The systematic review synthesized research on vegetation and soil carbon, and biodiversity in the Amazonian forests using PRISMA methodology. A total of 124 peer-reviewed studies published between 2000 and 2025 were analysed. Findings reveal vegetation and topsoil carbon have been extensively studied, while soil carbon, particularly in deeper horizons, remains underexplored. The maximum reported Aboveground carbon (AGC) was 375.18&#xa0;Mg C ha⁻¹ in upland forest of Guyana, 223.8&#xa0;Mg C ha⁻¹ in <i>várzea</i> floodplains of Amapá (Brazil), 108&#xa0;Mg C ha⁻¹ in <i>igapó</i> floodplain in Bolivar (Venezuela), 103.14&#xa0;Mg C ha⁻¹ in peatlands of Peru, and 260.9&#xa0;Mg C ha⁻¹ in Andean Cloud forests of Amapá (Brazil). Tree species richness in Amazonian forests spans from as low as 6 species ha⁻¹ in upland forests of Venezuela to as high as 292 species ha⁻¹ in upland Orellana, Ecuador, with notable ranges of 29–238 species ha⁻¹ in <i>várzea</i>, 16–153 species ha⁻¹ in <i>igapó</i>, 19–33 species ha⁻¹ in peatland, 40–201 species ha⁻¹ in swamps, and 20–160 species ha⁻¹ in white sand forests. A very high Shannon-Weiner Index (6.92) was reported for <i>Caraipa densifolia</i> Mart. (16.61% IVI) dominated upland forest in Bolivar, Venezuela. Fisher’s alpha was highest (160.3) for <i>Eschweilera coriacea</i> (102.1% IVI) dominated Colombian upland. <i>Igapó</i> (86.7) and <i>várzea</i> (95.1) had the highest functional richness across all Amazonian forest ecosystems. Soil organic carbon (SOC) content in topsoil was &lt;1% in upland forests of Peru and reached up to 51.9% in Peruvian peatland. Integrating vegetation and soil carbon and biodiversity assessments revealed significant relations between carbon and diversity (taxonomic, structural, and functional) of Amazonian forests.</p>