Changing public behaviour is an essential step for successful conservation, and can be achieved through effective use of message framing. However, its use in the conservation sector is not well-studied. We first performed a content analysis to assess what types of framing styles environmental non-governmental organisations (ENGOs) often employ for their social media posts. We then ran a real-world online fundraising campaign to examine the influence of value-framing (‘Intrinsic’ and ‘Extrinsic’) and message valence (‘Positive’ and ‘Negative’) on audience engagement with the advertisements, across five countries. Altogether, ENGOs generally used ‘Positive’ framing for their posts significantly more often than ‘Negative’, but did not use one type of value-framing more than the other. For the fundraising campaign, there were significant differences between countries’ engagement with the advertisements. However, click-through rates did not significantly differ when using types of value-framing nor message valence, and no donations were received to support the campaign. These results may show that message valence and value-framing alone have little influence on audience engagement, if any, at least in the context of social media. To enhance campaign success for the future, it is recommended that conservationists offer concrete information regarding fundraising outcomes, and activate social norms.