Majority of the current business models and production technologies are not only unsustainable, they are incapable of delivering long-term transition to low-carbon economy. Many firms are now looking beyond their internal knowledge boundaries in order to be competitive. Access to external knowledge through open innovation has thus been recognized as an important source of firm’s innovativeness. This even becomes more important for eco-innovative firms (EIs) as their knowledge bases are quite complex and diverse. As such, EIs must be willing to pursue an innovation strategy with a large portfolio of external knowledge inputs. As critical as this issue is, few evidence exist on how EIs access both synthetic and analytic external knowledge for competitive advantage. The main objective of this proposal therefore, is to examine the dynamics of alliance portfolio or external knowledge sourcing strategies for eco-innovation in the manufacturing and service sectors of Nigeria using both qualitative and quantitative data. The research will investigate and answer questions such as: to what extent do firms in Nigeria search for knowledge outside their competence before absorbing and internalise such external knowledge to eco-innovate? Is there a threshold beyond which deep search for external knowledge diminishes propensity to eco-innovate? Does R&D reduce cognitive distance between external knowledge providers and EIs? Data will be collected from the firms in both sectors using questionnaire and structured interview guide. The study will use stratified sampling technique to select firms using the National Bureau of Statistics and the Nigerian Stock Exchange registers as sampling frames. The study will borrow from evolutionary economics and national innovation system framework to analyse and discuss some of the findings. This study would contribute to policies that would remove institutional and policy barriers to inclusive and sustainable private sector driven green growth.