Indicators are crucial for any management as they allow for monitoring, reviewing and adapting strategies towards a previously planned objective. The key challenge for fulfilling this task is to identify and define indicators that enable the assessment of the system under consideration. Regarding energy systems, if understood as complex socio-technical systems, a multitude of indicators for resilience assessments have been proposed, which vary according to the different systems analysed as well as indicators and stakeholder requirements. Hence, it seems that universal indicator frameworks are not applicable for resilience assessments and thus specific indicators are needed. However, a crucial step towards developing a general resilience assessment and monitoring framework is to understand on which aspects indicators depend, what “good” indicators can cover and what the limits of these indicators are. Therefore, this chapter gives an insight into the general characteristics of indicators. Then, it describes the indicator requirements particularly with respect to the resilience (monitoring) for energy systems. Furthermore, the chapter will address some specifics for the resilience assessment and management of energy systems based on some exemplary indicators.