Although research on corporate social responsibility (CSR) has grown steadily, little research has focused on CSR at the individual employee level within cultural heritage tourism. This article sheds light on the antecedents of employee environmental behaviour and the effects of a social marketing intervention in a tourism organisation using a mixed methods longitudinal approach. Qualitative results (from 68 respondents) suggest knowledge and awareness of environmental solutions are often lacking while quantitative results (from two surveys with 237 and 96 employees) highlight the influence of motivations, perceived potential to change and perceived information adequacy on employees’ satisfaction with their environmental behaviour. Additionally, a proxy measure of actual behaviour change, energy usage, is reported, highlighting the intervention’s success in changing actual behaviour. The paper highlights the need for managers to increase knowledge and self-efficacy and to carefully consider how varying motivations and barriers might explain differences across organisational sites when designing interventions.