Since the introduction of magnetic extraction sorbents in 1996 by Towler et al., magnetic nanoparticles (m-NPs) have gained importance as sorbents in sample preparation procedures, especially in the so-called magnetic-dispersive solid-phase extraction (m-dSPE), as a result of the simplification of the extraction procedure, which saves time and efforts. Despite the fact that m-NPs have been used in some cases as synthesized, without any further modifications, they do not generally have enough extraction capacity for organic analytes and have a high tendency to aggregate as well as a high chemical reactivity, which results in a loss of dispensability and magnetism. As a result, they are generally coated with different materials (i.e., silica, surfactants, ionic liquids, antibodies or aptamers, polymers, carbon nanotubes, molecular organic frameworks, etc. or their mixtures) which enable them to selectively and quantitatively extract a good number of organic analytes from different matrices. The aim of this chapter is to review the current state-of-the-art of the application of coated/functionalized m-NPs in sample pretreatment, especially in m-dSPE, providing a critical and updated overview of the different m-NP coatings and their effectiveness for organic analyte extraction.