Impact indicators are systems/organisms, the vitality of which alters in response to changes in environmental condition. The indicators assessed in this review fall within the impact category of the driver-pressure-state-impact-response (DPSIR) framework. Instrumental records have shown unequivocal changes in climatic conditions over the past 30 years at a global level but impact indicators allow these changes to be monitored at a finer resolution. Our main aim was to review sets of indicators of climate change currently used in various countries and to make recommendations for their use in the Irish environment. We review a preliminary set of climate change impact indicators in five sectors: agriculture; plant and animal distribution patterns; phenology; palaeoecology and human health. Currently, the most effective impact indicators of climate change have proved to be phenological observations of tree developmental stages. The strongest factor limiting the use of indicators is the lack of long-term data sets from which a climatic signal can be extracted.