This chapter presents an overview of biomarkers and ecological indicators used to measure radiation stress in invertebrates. Using examples, we will show how and in what context the different biomarkers can be used and on which invertebrate species. We will also describe how the biomarker techniques can be adapted from other taxa including humans and developed for use in invertebrate species. Biomarkers generally fall into two categories - biomarkers for exposure and effect. Invertebrates have not frequently been used to investigate radiation-induced stress but they offer great potential. Here, we present biomarkers that have been used in different ecotoxicological contexts and are appropriate for measuring radiation exposure: comet assay, micronucleus assay, cytochrome p450 and oxidative stress. The majority of previous studies that have used biomarkers for environmental stressors have been conducted on either mussel for aquatic systems or earthworms in terrestrial systems. We also present an overview of how ecological indicators benefit understanding of the consequences that radiation exposure to individuals living in contaminated environments, focussing on alterations to reproduction and behaviour.