Direct and indirect effects of climate change may have substantial impacts on plant defences against herbivory. However, there are limited long-term historical data on plant morphological and chemical defences, making it difficult to quantify temporal shifts in plant defences in response to climate change for species growing in natural environments. We were able to access historic defence trait data by growing plants from resurrected, ex situ, stored seeds collected 24–40 years ago, and we compared this to plants grown from matched collections of modern seeds of the same species. Using a novel method - ‘Climate Contrast Resurrection Ecology’ - we grew historic and modern seeds in a glasshouse for 31 plant species from a range of sites, some of which had undergone substantial climate change, and some of which had not. We then related differences in defences between modern and historic plants to changes in the local climate (including changes in: mean temperature and precipitation, variability in temperature and precipitation and climatic extremes including heatwaves, droughts and dry spells and aridity) where the species’ historic and modern seeds were collected. We predicted that defences would have changed more in species whose seeds were collected from sites where the climate had changed more. We found substantial changes between the historic and modern populations in plant defence traits including leaf thickness, phenolics, lipids, ash and carbon-to-nitrogen ratios. On average, the defence traits we measured showed similar amounts of absolute change as morphological and physiological traits measured using the same methods. However, changes in defence traits were not significantly related to changes in the climate of the species’ populations. Changes in plant defence traits may be more directly influenced by herbivory, and could be affected by interactions between biotic and abiotic factors that are potentially complex.