Abstract A growing body of evidence shows that climate change can alter the phenology of plants and animals. In this study long-term data from the UK Environmental Change Network (ECN) were analyzed to investigate whether there has been a change in the phenology of the ground beetle Pterostichus madidus (Fabricius, 1775). Pitfall trap data were available from 12 ECN sites across the United Kingdom, most of which have been in operation for more than 15 years. Weather and vegetation datasets were also utilized. Pitfall trap lines were categorized to eight vegetation types. Trend analysis over time was carried out first using all the available dates of capture events, then the datasets grouped by vegetation type and site. Shifts in high-activity periods were also analyzed. P. madidus appearance dates advanced significantly at seven sites and in five vegetation types. Peak activity advanced at two sites. At one site the timing of activity became significantly later. The last day of activity did not change significantly, supporting the theory that the cessation of the activity period is more likely to be controlled by photoperiod than temperature. The relationships between phenological variables and climatic factors were also investigated. However, no significant correlations were detected. These results demonstrate that between 1992 and 2008, phenology of P. madidus at seven sites from the eight analyzed has changed. Global warming may be driving these changes and future work will investigate underlying processes.