This dataset presents sedimentological, geochemical, and subfossil Chironomidae data from a mangrove core collected at Ilha Grande, Rio de Janeiro State, southeastern Brazil (approx. 23°S, 44°W). The record includes head capsule counts of Chironomidae separated into three size fractions (>250 µm, 250–88 µm, and 88–74 µm), along with sediment density, chronological information, and concentrations of major and trace elements (e.g., Al, Fe, Mn, Pb, Zn, Ti, Si, P, S, and others). Linear and power-based air temperature reconstructions (°C) were derived from Chironomidae assemblages using transfer functions developed for tropical regions. The core was sampled in 2023 and dated using combined ²¹⁰Pb analyses with CRS model, covering approximately the last 170 years (1860–2024 CE). Sediment slices of 1 cm were analyzed for biological and geochemical parameters to assess recent environmental and climatic variability in tropical coastal ecosystems. Chironomidae head capsules were extracted using standard subfossil preparation protocols, mounted under optical microscopy, and identified to morphotype level following Walker (2001) and Brooks et al. (2007) with aditional personal modifications. Elemental concentrations were determined via X-ray fluorescence (XRF) spectroscopy, and total density was measured gravimetrically.