Internationally-agreed sustainability goals are being missed. Here, we show how the extent to which humans see themselves as part of nature –known as human-nature connectedness (HNC) –can be used as a leverage point for reaching sustainability. We conduct the first global meta-analysis of the HNC literature. Meta-analysis of 147 correlational studies documents that individuals with high HNC had more pro-nature behaviours and were significantly healthier than those with low HNC. Meta-analysis of 59 experimental studies documents no effect of environmental education on HNC while HNC significantly increased after manipulations involving contact with nature and mindfulness practices. Thus, HNC is positively linked to mindsets that value sustainability and behaviours that enhance it. Further, we show that HNC can be enhanced by interventions and we identify techniques most likely to succeed. These results suggest that enhancing HNC, via promotion of targeted practices, can improve sustainability and should be integrated into conservation policy.