The increasing presence of abandoned, lost, or discarded fishing gear (ALDFG) on the seafloor is a major source of microplastics (MPs) pollution in coastal ecosystems. This study assessed the concentration, morphology, and chemical composition of MPs in surface sediments collected from Alicante and Benidorm, in the Valencian Community, eastern coast of Spain, Mediterranean Sea. Impacted sites with fishing nets were compared to control sites without nets. Two analytical techniques were used for polymer identification, depending on particle size: micro-Fourier Transform Infrared Spectroscopy (µFTIR) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (FTIR-ATR). The results showed significantly higher MPs concentrations in sites affected by ALDFG. The findings highlight a clear link between the presence of fishing nets and MPs accumulation in sediments. This underlines the urgent need for mitigation strategies and recovery of discarded fishing gear. This study addresses a gap in the literature regarding MPs contamination on rocky coastal substrates and calls for further research to assess the long-term ecotoxicological impacts on marine ecosystems.