Cross Sector Social Partnerships are often portrayed as mechanisms of democratic participation of all involved parties. Hence the role of accountability is prominent in safeguarding that the voices of the internal and external stakeholders are being heard. In a nonprofit-business partnership the role of the nonprofit organisation is important in safeguarding social standards and high quality programme implementation. The paper presents empirical findings from an in-depth partnership case study between a mining company and an environmental nonprofit organisation. The analysis identifies the missed opportunities of employee involvement at the nonprofit partner under the three stages of partnership implementation: selection, design and institutionalisation. The paper offers recommendations for strengthening the internal accountability mechanisms in order to safeguard corporations’ CSR investment and the accountability of nonprofit organisations.