In this chapter we review the available data on the application of non-targeted high-resolution mass spectrometry (HRMS) analysis to identify a wide range of substances (mainly emerging pollutants) present in sludge. We focus on non-targeted workflows developed with these instruments: (1) the screening of suspects or broad screening and (2) the analysis of unknown compounds providing a fingerprint of almost all chemical contaminants present in sludge. The different workflows as well as their achievements and pitfalls within the identification of chemicals in sludge are discussed in depth. The pre-treatment of sludge (decisive for the detection of compounds) is also discussed since it cannot be avoided due to the complexity of the sample.