Research expedition M124 took place from February 29th to March 18th 2016, saling from Cape Town, South Africa to Rio de Janeiro, Brazil. CTD data for 16 stations with a total of 52 individual casts along the cruise track were recorded using a Sea & Sun Technology CTD90M (SN 979), attached to a HydroBios Multi-Plankton-Sampler, down depths of 700m. The CTD was equipped with sensors for temperature (Pt100 model 1509, Thermal Developments International), conductivity (7-pole platinum coated electrode cell in quartz glass, Sea & Sun Technology) and chlorophyll a (Seapoint Chlorophyll Fluorometer, Seapoint). The data files contain the data for temperature, salinity, density and chlorophyll a concentration; as raw data and processed and flagged according to the recommendations for real-time data processing of EuroGOOS and GTSPP, as well as the outlier detection method CoTeDe (https://github.com/castelao/CoTeDe). Biogeographic regions are determined according to Spalding et al. (2012). TEOS-10 unit conversions have been performed with the GSW Oceanographic Toolbox (McDougall and Barker, 2011).