ClimateWatch is a citizen science project developed in 2009 by Earthwatch to understand how climate change is affecting the seasonal behaviour (or phenology) of Australia's plants and animals. ClimateWatch gives every Australian the opportunity to participate in a long-term climate change study. Observations can be made at one of over 70 ClimateWatch trails across the country (www.climatewatch.org.au/trails), or anywhere else in Australia (backyards, school grounds or parks and reserves). Observations are recorded using a smartphone application or online web platform. Over 140 species of plants, birds, mammals, reptiles, insects and marine flora and fauna are currently being monitored. Species selection (http://www.climatewatch.org.au/species) has been supported by the ClimateWatch scientific advisory panel to study changes in species location or seasonal behaviour. Observation methodologies and details about the project are outlined at www.climatewatch.org.au.