AfSIS Phase I was a collaborative projective funded by the Bill and Melinda Gates Foundation (BMGF), which aimed to provide a consistent baseline of soil information for monitoring soil ecosystem services in sub-Saharan Africa (SSA). Partners included, CIAT-TSBF, ISRIC, CIESIN, The Earth Institute at Columbia University and World Agroforestry (ICRAF). The Land Degradation Surveillance Framework (LDSF), developed at ICRAF, was employed to systematically sample key biopshyical indicators of land and soil health, across landscapes. LDSF sites were randomized using spatial stratification based on Koeppen-Geiger Climate zones across 19 countries in SSA. Soil samples were collected using the LDSF at two depths, 0-20 cm and 20-50 cm. Mid-infrared diffuse refectance spectroscopy (MIR) was a key soil characterization and screening tool in AfSIS. MIR measurements of the ~18,500 samples were centralized at ICRAF’s Soil-Plant Spectral Diagnostics Laboratory based in Nairobi Kenya using the Bruker Tensor 27/HTs -XT_FT-IR. The MIR dataset is provided here, organized by country.