This paper reports on the outcome of two workshops on this issue that took place in Cape Town, South Africa in 2004 and 2013. In 2004, the objective was to review the concept of biodiversity mainstreaming, to promote best practices in GEF projects focused on production landscapes and seascapes, and to assess the effectiveness of such interventions. In 2013, the objective was to assess lessons learned, and includes case studies and perspectives on mainstreaming. The report concludes that while progress has been made to mainstream biodiversity into broader policy and practice areas, it is clear that more care needs to be brought to the design, implementation, and assessment of mainstreaming projects to inform and improve future efforts.