Gasification is an attractive treatment for valorization of sewage sludge since it allows converting a waste, whose disposal is environmentally and economically challenging, into a resource. Indeed, during the last decades, sewage sludge disposal has become of the most important problems for wastewater treatment plants together with the high energy demand associated with the processes. In this context, gasification of sewage sludge aimed at energy recovery could be significantly advantageous. For this reason, this chapter aims at analyzing the current state of the art related to sewage sludge gasification focusing on its impact on sustainable valorization of the sludge. The work will deeply assess the main parameters that affect gasification efficiency, such as the type of reactor, gasifying agent, operating parameters of temperature and equivalence ratio, and the eventual impacts of catalysts application on process performances. Also the effect of these parameters on the process outcomes will be considered. Moreover, possible applications for the process outputs, syngas and biochar, will be examined, highlighting the environmental and economic benefits of their reuse and/or recovery. Then, to practically demonstrate the feasibility of sludge gasification as well as its advantages and drawbacks, a case study will be investigated. Finally, considering the main results of the analysis carried out, the challenges for widespread diffusion of sludge gasification will be illustrated together with the opportunities of implementing this process.