The way business has been conducted in modern times has traversed the need to achieve financial gains. Globally, it has become imperative for organisations to thrive competitively on the basis of ecologically conciousness and sustainability. Hence, the primary aim of this investigation is to determine how Eco-Intellectual Capital (EIC) influences the sustainability performance of small and medium enterprises (SMEs). The study made use of primary data and employed a quantitative research approach using a survey for data collection. The main data collection instrument used was a structured questionnaire. Data for the study were solicited from a group of 500 employees and owners managing SMEs in Ghana. Data collected from the questionnaires were analysed using IBM SPSS Statistics version 24 and IBM SPSS AMOS (26.0) Graphics. The results showed that EIC had a favourable effect on the social and environmental dimensions of sustainability performance. On the economic (financial) dimension, however, the effect was not significant. Aside from magnifying Eco-Intellectual Capital and Sustainability Performance literature, this research study is one of the few that looks at how green human, structural and relational capital work together to improve the economic, social and environmental sustainability of SMEs in emerging economies.