Sustainable development deals with grand challenges related to human well-being and environmental sustainability. Assessing sustainability initiatives goes beyond technical solutions and requires the engagement and deliberation of multiple stakeholders. Participatory modelling is a promising approach to explore sustainability alternatives by using technical tools (e.g. simulation) while actively involving stakeholders. The discussion around sustainability alternatives has ethical implications as it deals with matters that affect people and the environment. However, despite ethical aspects are implicit in participatory modelling processes, they are often overlooked. This study aims to make visible the ethical dimension of participatory simulation models in the context of sustainability. Here we propose to have sustainable development and human rights as ethical standpoints for participatory modelling efforts in complex social-ecological settings. A practical-oriented ethical evaluation is proposed in the form of questions structured across a relevant participatory modelling framework. An ethical lens is essential to guide social-ecological systems modelling throughout to identify pathways that align with principles aiming to protect human dignity, promote justice, and prevent environmental harm. The proposed ethical framework aims to promote the design of socially accepted and ethically transparent models that support decision-making processes aligned with the Sustainable Development Goals (SDGs) transitions.