The widespread occurrence of microplastics (MPs) in soil-like materials (SLMs) at landfill sites presents significant geoenvironmental concerns, necessitating reliable evaluation techniques. This study employs a combination of image-based classification and chemical analysis to assess MPs concerning their dimensions, morphology, abundance and oxidation levels, thereby addressing the ecological risks posed by their degradation. Initially, manually retrieved plastic samples from SLMs were processed using image analysis to establish reference metrics. MPs were extracted via dual-density separation using NaCl and ZnCl₂ solutions, following organic matter removal. High-resolution images obtained with a Nikon DSLR camera were converted to 8-bit greyscale and subjected to thresholding to evaluate parameters such as size, aspect ratio, circularity, and solidity. Further oxidation level assessment was conducted through FTIR spectroscopy by computing indices such as the Carbonyl Index (CI) and Hydroxyl Index (HI). The automated image-based characterisation demonstrated an efficiency of 80–95% compared to manual analysis, thereby improving the precision and consistency of MP quantification. FTIR spectra identified polyethylene, and polypropylene as dominant polymer types, highlighting their oxidative deterioration. These results underscore the effectiveness of an integrated approach to MP assessment and its potential to mitigate environmental hazards associated with oxidised MPs in landfill settings.