Investing in organisational development (OD) to improve impact and sustainability is critical. However, a lot remains to be done for funders and NGOs to more intentionally invest in OD to build a stronger, more resilient NGO sector. This is a long-term journey that requires a commitment from NGOs and funders to engage in honest reflection and continuous action. This toolkit provides some initial guidance and resources to stakeholders in the sector to advance impact through OD.