As proposed by the Addis Ababa Action Agenda as well as other documents published by international organizations, the involvement of the financial sector will be indispensable in achievement of the SDGs. And the integration of holistic impact analysis in financial institutions' business process, suggested the UNEP FI, can support the shift to an impact-based economy and close the SDG financing gap. However, there are also concerns over the effectiveness and risks of involvement of the financial sector and private businesses in development fields. The thesis is based on a literature review on sustainable finance topics, research into best practices of impact management promoted by different initiatives, and the insights from a 6-month full-time internship with the Positive Impact Initiative in United Nations Environment Programme Finance Initiative (UNEP FI). The thesis discusses the role of the financial sector in achievement of the SDGs and the motivation and difficulties for mainstream finance.