Green is gaining importance in the software realm at the present time. Many efforts to obtain sustainable software are being undertaken; as a result, new techniques for producing “Green software” are now appearing. Nonetheless, there is a huge amount of existing software which is not following greenability principles (reduced impact on economy, society and environment). This fact leads to the question “Is there any way to improve the greenability attributes of an existing software?” The key point in offering a solution to this problem lies in one of the most important stages in the software life cycle: Software Maintenance. Software Maintenance not only allows us to solve software problems and improve quality but also enables us to refactor transformations in order to improve certain software characteristics. This chapter offers an overview of what kind of techniques, tools and practices could be useful in software maintenance in the quest to improve software greenability in existing software systems.