Portfolio management is a complex problem that involves the complexity of the interdependent projects and programs. Portfolios are where resources are distributed in an optimal manner to achieve the organization’s objectives. However, risks can arise from all levels of an organization, such as from individual projects or the entire organization, that can endanger the company’s goals. Having said that, risk management methods target risks at each individual level and consider different risk factors. Therefore, a holistic risk management approach is needed that combines risk factors from all levels. This thesis aims to identify risks from strategic, portfolio and project levels that contribute to the overall portfolio risk. By applying an extensive systematic literature review we highlight different frameworks and current best practices. The presented work can serve as a tool for managers to further reduce risk within their organizations.