I have examined whether the practice of social investing by private trustees is consistent with their fiduciary duties of prudence and loyalty. I have reviewed American, British and Canadian jurisprudence and statutes to compare and contrast those jurisdictions' legal positions so as to resolve the tensions created by the practice of social investing.In private trust law, the trustee's only concern should be to safeguard the financial interests of the beneficiaries and not to promote the social agenda of the trustees or of a third party. Social investing entails making investments on the basis of non-financial criteria. I have examined whether a settlor's direction to a trustee in the trust instrument to practice social investing is consistent with the trustee's fiduciary duties. I have also suggested two potential solutions to the conflict: the acceptance of a limited version of social investing and the creation of an ethical statutory trust.