The dataset contains chemical analyses from the well-characterised Hakgala field site in the tropical Highlands of Sri Lanka. This site is located on a road cut between Nuwara Elia and Welimada (06.92923° N, 80.81834° E, 1753 m altitude), bordering a 12 km^2 natural forest reserve consisting of pristine, mature, stable upper montane rain forest, close to the Hakgala Botanical Garden. A deeply weathered regolith depth profile (ca. 10 m) developed on a hillslope underlain by charnockite bedrock. Adjacent to the regolith profile ecologically pristine catchments (>1 km^2) are drained by small creeks. Here, data on samples of all compartments of the Critical Zone (defined as the near surface layer of the Earth extending from the bottom of the weathering zone to the top of the tree canopy) are reported. The dataset compiles published (Hewawasam et al., 2013, GCA, 118, 202-230) and new data (Schuessler et al., 2018, Chemical Geology) of element concentrations, stable Mg isotopes, and radiogenic Sr isotope ratios on stream water (time series sampling 2010-2013), vegetation, soil, saprolite (depth profile sampling), weathered bedrock (corestones), and unweathered bedrock. From this data, weathering indicators such as the chemical depletion fraction (CDF) and the element mass transfer coefficients (Tau) were calculated and reported in the dataset. The samples used for these analyses have been assigned with International Geo Sample Numbers (IGSN, www.igsn.org). Details on sampling locations are provided via IGSN links in the tables and in the related work section on the DOI Landing Page at GFZ Data Services. Moreover, the IGSN data can be accessed by adding the IGSN after igsn.org, e.g. igsn.org/GFFB1003V. Further details on sampling and locations are provided in Hewawasam et al. (2013, GCA, 118, 202-230). This publication contains an annotated summary table serving as a supplementary table for Schuessler et al. (2018, Chemical Geology) in pdf and xlsx (Microsoft Excel) formats. In addition, separate tables reflecting differing samples and methodologies for input into statistical software are provided as comma separated files. Column headers for all tables are explained in a separate csv file (Data columns headers for tables S1 to S3.csv). The analytical methodologies used to generate the data are described in the data description file.