International opportunity is a burgeoning theme in international entrepreneurship research evolving through cross-fertilisation of entrepreneurial opportunity and international business research. A majority of exploratory work on international opportunity recognition or creation stems from the conceptual extensions of entrepreneurship literature. This study addresses recent calls (Mainela et al., 2014; Muzychenko, 2011; Schweizer et al., 2010) for advancing research on international opportunity enactment by small and medium-sized enterprises (SMEs). In this study, two theoretical perspectives of the theory of planned behaviour and the dynamic capability framework are applied to investigate whether or not, and the extent to which, the key decision maker’s cognitive attributes and the firm’s dynamic capabilities influence international opportunity enactment. The United Kingdom, as a developed economy with many internationalised SMEs, provided a vibrant context in which to conduct this study. International opportunity enactment is defined as the act of seizing international opportunities. In this study, international opportunities include opportunities for international market entry, new products/services development for international markets, and new process development for international markets. The study proposes that if an SME has high learning, relational, and innovation capabilities and its key decision maker has a positive attitude, intention, and self-efficacy, then the SME is more likely to enact international opportunities. This study adopted a mixed method research approach collecting and analysing both quantitative and qualitative data. First, a survey was conducted on a representative sample of ninety-one exporting SMEs within the UK. Quantitative data analysis was conducted through Partial Least Squares (PLS) structural equation modelling. The findings were then triangulated with qualitative data collected from five case studies. Data from the case studies was analysed in a deductive manner to evaluate the findings of the quantitative data analysis. The results of the analyses indicated that a key decision-maker’s self-efficacy and a firm’s learning and innovation capability can exert a positive influence on international opportunity enactment. The decision maker’s positive attitude and intentions are common attributes among participants regardless of the magnitude of international opportunity enactment. Additionally, a firm’s high relational capability supports creating new international relations, but in highly committed relations firms tend to serve existing international customers rather than taking up more international opportunities. The originality of this study lies in its effort to integrate insights from the management literature with that of the entrepreneurship literature in the thematic area of international opportunity. It highlights the role of firm-level capabilities alongside the individual key decision maker’s cognitive attributes as the drivers of international opportunity enactment. The findings of the study contribute to three specific areas of scholarship within international entrepreneurship: (1) international opportunities: it identifies four factors that positively influence international opportunity enactment with supportive empirical evidence; (2) the dynamic capability framework: it shows that the dynamic capability literature is well suited to explain the enactment of international opportunities; and (3) the theory of planned behaviour: here the study shows that in contrast to the present understanding, the attitude and intention of the key decision makers have very little influence on the enactment of international opportunities. In the light of the findings, and given the limitations of the study, some areas for future research are offered. The study also proposes some managerial implications that can help SMEs in their internationalisation journeys.