Due to the many factors controlling δ13C values in stalagmites, complicating their paleoclimatic and paleoenvironmental interpretation, most studies do not present δ13C values, but instead focus mainly on δ18O values. This is also the case for most cave studies from tropical South America, where many new δ18O stalagmite records covering the last millennia were recently published. Here, we review the δ13C values in stalagmites, investigating the influence on this proxy of local hydroclimate, altitude, temperature and vegetation types, by employing a new dataset composed of published and unpublished carbon isotope records from various sites in tropical South America. The main factors influencing δ13C values are associated with the local hydroclimate, followed by minor effects from temperature. Most of the isotopic records show a significant correlation between the δ13C and δ18O values, indicating a close relationship between local hydroclimate and atmospheric convective processes related to the South American Monsoon System.