The phenomenon of international entrepreneurship (IE) gained prominence in the mid-1990s, greatly stimulated by globalization, digitization of the economy and the creation of institutional conditions favouring entrepreneurs. When combined and allied to various intangible assets developed by firms, these factors stimulated the identification and exploitation of business opportunities on a global scale, giving rise to the academic field of IE. Despite the apparent maturity of this field of study, only in the last decade has the academic community increased the number of publications, diversifying them, introducing new sub-topics and making it a field that should be studied and addressed from various lenses. Therefore, this thesis aims to explore various facets of IE, contributing to its consolidation and progress, approaching the topic from a multi-level perspective: macro, meso and micro. This is done over seven chapters. The first chapter is the general introduction of the thesis, describing the problem and the study context, the aims, the research design and methodology, the contribution and other aspects. The second chapter presents a Systematic Literature Review (SLR), entitled “International Entrepreneurship: a systematic review and future research agenda”. This chapter discusses the state-of-the-art of IE, reviewing the main studies that contributed to developing the area. To do so, the Web of Science (WoS) and content analysis techniques were used to give a holistic perspective of this field of study and identify new topics introduced in recent years and lines of convergence. IE was found to be concentrated fundamentally in four thematic groups: i) institutional environments, ii) drivers and process of internationalization, iii) international business opportunities and networks, and iv) entrepreneurs’ characteristics and motivations. An integrative framework was also developed to access, albeit in a simplified way, the status of IE research and understand how the diverse themes are inter-related. This SLR was determinant in advancing various topics for future lines of research, detailed by the thematic group, providing the structure of the chapters in this thesis. Therefore, the topics of the chapters forming the thesis were based on a future line of research for each of the four thematic groups/clusters detailed below. The third chapter, “Business environment reforms’ effect on the entrepreneurial activities of high-income economies: panel of the evidence” (cluster 1) deals with the activities. Specifically, the intention is to examine whether the reforms carried out by institutions in high-income economies, aiming to benefit the business environment, in fact led to higher rates of entrepreneurship. To this end, a longitudinal study was carried out using panel data for the period from 2010 to 2019, based on two secondary databases, namely ten indicators proposed by Doing Business (World Bank) and Total Early-stage Entrepreneurial Activity (TEA), by Global Entrepreneurship Monitor (GEM). The results showed that only the reforms carried out in three indicators of Doing Business – Dealing with Construction, Registering Property and Enforcing Contracts, affect TEA positively. The remaining indicators, Starting a Business, Getting Credit, Protecting Minority Investors and Paying Taxes, showed no significance, while the indicators of Getting Electricity, Trading Across Borders and Resolving Insolvency had a negative impact on TEA. This study points out important considerations for international and local entrepreneurs, as well as policy-makers, warning of the ineffectiveness of some measures introduced and the need to reconsider reforms. The fourth and fifth chapters focus on organisational (meso) dimensions considered relevant to develop intangible, strategic assets, giving Small and Medium-sized Enterprises (SMEs) early access to international markets, but also aiming for good levels of competitiveness and performance. The fourth chapter is entitled “International Entrepreneurial Culture: capturing differences between Born and non-Born Globals” (cluster 2). This chapter addresses International Entrepreneurial Culture (IEC), still a little-explored topic in terms of research. In particular, it seeks to capture differences in five dimensions of IEC (International Entrepreneurial Orientation [IEO], International Market Orientation, International Motivation, International Learning Orientation, International Networking Orientation) between born globals and non-born globals (late exporters). Primary data were collected from applying a questionnaire to 168 internationalized SMEs in Portugal, using MANOVA as the statistical technique to determine whether these groups present statistically significant differences in the dimensions of IEC. As results, this chapter revealed that born globals show differences from their non-BG counterparts in terms of autonomy, international motivation and orientation to the international market. Theoretical and practical implications are also presented for company managers aiming for early internationalization. The fifth chapter is entitled “The role of International Entrepreneurial Orientation for Early Internationalizing Firms: Moderating effects of International Networking” (cluster 3). This chapter sought to analyse the moderating effect of International Networking Orientation (INO) on the relations between the dimensions of IEO (risk, innovation, pro-activeness, competitive aggressiveness and autonomy) and early internationalization. To this end, a questionnaire was applied to a sample of 171 Portuguese SMEs, of which 96 are Early-internationalizing Firms (EIFs), and 76 are late exporters. The results showed that innovation, autonomy and competitive aggressiveness are variables at the origin of early internationalization. In addition, INO with competitors was found to present a positive interaction in the relation between pro-activeness and EIFs and a negative relation between these firms and risk-assumption. These results can help firms to configure their intangible assets in early internationalization processes. The sixth chapter deals with IE at a micro level, analysing the role of entrepreneurs and managers’ knowledge and dynamic capacities in International Business (IB), regarding the possible returns arising from international experience. It is entitled: “Knowledge and capabilities: what are their roles in SMEs’ international business?” (cluster 4). This study adopted a qualitative approach through ten semi-structured interviews with entrepreneurs in various industries. The results showed that knowledge and dynamic capabilities are determinants for the development of international activities. Furthermore, a presence in international markets was determinant for acquiring new knowledge and exploiting the new learning capabilities developed, which are essential to operate in domestic and other international markets. The thesis has one final chapter, which discusses the general conclusions, contributions and future lines of research. As contributions, the thesis combines a set of studies highlighting that IE, although a complex phenomenon, is increasingly present for SMEs with limited resources. It is suggested that these firms should develop and implement, at the organisational and individual level, a set of intangible strategic assets as a way to reach international markets at an early stage and quickly, aligning them with various typologies of knowledge and dynamic capabilities. Entrepreneurs are also informed that the conditions for successful international ventures depend on a favourable business environment provided by government institutions, marked by regular and effective reforms. To summarise, this thesis advances the perspective that IE is stimulated when organisations’ internal and external factors interact and complement each other, providing various orientations for policymakers, organisations, entrepreneurs and academics.