Climate change is one of the biggest threats to humanity. Scientists are well-positioned to help address it beyond conducting academic research, yet little is known about their engagement with the topic. We investigate scientists’ engagement with climate change using quantitative and qualitative analyses of a large-scale survey (N = 9,220) across 115 countries, all fields, and all career stages. Many scientists already engage in individual lifestyle changes, but fewer engage in advocacy or activism. Based on the qualitative and quantitative responses, we propose a two-step model of engagement to better understand why. Scientists have to overcome intellectual and practical barriers to first be willing to engage, and then different barriers to actually engage. Based on this model, we provide concrete recommendations to increase the engagement of scientists with climate change.