This Handbook provides recommendations for the implementation of an Agile approach in space software projects complying with EN 16603-40 (ECSS-E-ST-40) and EN 16602-80 (ECSS-Q-ST-80). This handbook is not an Agile development book, though it provides an Agile reference model based on Scrum and also covers other major Agile methods and techniques. Scrum has been selected as reference because of its widespread application in industry and its flexibility as a development framework to introduce or merge with other Agile methods and techniques. In relation to the ECSS-E-ST-40 and ECSS-Q-ST-80, this handbook does not provide any tailoring of their requirements due to the use of the Agile approach, but demonstrates how compliance towards ECSS can be achieved. This handbook does not cover contractual aspects for this particular engineering approach, although it recognises that considering the approach of fixing cost and schedule and making the scope of functionalities variable, the customer and supplier need to establish specific contractual arrangements. Furthermore, it does not impose a particular finality for the use of Agile, either as a set of team values, project management process, specific techniques or supporting exploration by prototypes. This handbook, covers, in particular, the following: " In clause 4, the fundamentals and principles of Agile. It also describes major Agile methods and general issues of implementing an Agile approach. " In clause 5, the criteria for selecting an Agile lifecycle. " In clause 6, a reference process model based on Scrum to be used to map its elements to relevant clauses of ECSS-E-ST-40. " In clause 7, guidelines for software project management, providing advice for ECSS-E-ST-40 clause 5.3 considering the reference process model based on Scrum. " In clause 8, guidelines for software engineering processes, providing advice for ECSS-E-ST-40 clauses 5.2, and 5.4 to 5.10, considering the reference process model based on Scrum. " In clause 9, guidelines for software product assurance and software configuration management, providing general advice for the implementation of ECSS-Q-ST-80 and ECSS-M-ST-40 with an Agile approach. Individual agile practices, introduced in this HB, can also be taken on-board in other software development life-cycles.