This dataset compiles geochemical parameters from measurements on samples that were collected during the Yukon Coast 2024 expedition (YC24). Terrestrial and marine sediment samples were taken on Qikiqtaruk–Herschel Island and the mainland Yukon coast in July 2024. Terrestrial samples originate from various depths of active layer, permafrost, and different zones within a retrogressive thaw slump (RTS). Marine samples were taken along a transect of the outflow of a RTS with a Van Veen grab sampler or a gravity corer. We analyzed the samples for dry bulk density (DBD), grain size distribution, and their content of mercury (Hg), methylmercury (MeHg), total organic carbon (TOC), total inorganic carbon (TIC), and total nitrogen (TN). All samples were frozen and stored under dark, air-free conditions until analysis. Whenever possible, samples were taken with a known volume to determine DBD. The sediments were freeze-dried with a temperature of 35 °C at the heating plates and split into three subsamples. One subsample was ground for Hg, TOC, TIC, and TN analyses using a planetary mill. For Hg, a Milestone Direct Mercury Analysis System (DMA-80 evo, MWS-GmbH) was used. TOC and TIC were measured with an ELEMENTAR soli TOC cube, and TN was determined using an ELEMENTAR rapid MAX N exceed. The second subsample was ground with a coffee grinder for MeHg analysis to allow for better temperature control while grinding. MeHg was extracted from the sediment using Dichloromethane (CH2Cl2, DCM) and then purged from DCM with nitrogen gas. The analysis was conducted with a Tekran® Model 2700 Methyl Mercury Analyzer connected to an Inductively Coupled Plasma Mass Spectrometer, thermo scientific iCAP TQ (ICP-MS). The results from the ICP-MS were converted into MeHg concentrations via signal deconvolution. The third subsample was left unprocessed for grain size analysis. Hydrogen peroxide (H2O2) was used to remove organic material prior to analysis, which was conducted with a Laser particle counter Mastersizer 3000 (MALVERN).