This document provides a toolkit for fund managers on integrating environmental, social, and governance (ESG) considerations into their investment processes. It discusses the business case for ESG analysis, including growing stakeholder expectations, regulatory trends, consumer demand for sustainable products, and evidence that ESG programs can improve financial performance and shareholder value. The toolkit is intended to help fund managers implement the British development finance institution CDC's investment code on ESG matters. It provides guidance on international ESG standards and tools to assess and manage ESG risks and opportunities at various stages of the investment process.