**Abstract**

The application of Web 2.0 social media in eCommerce and e-marketplaces (ECEMs) in developing countries has been on the increase in recent times especially during Covid19 and beyond. However, it is still unclear what theoretical foundations and factors guide ECEM in small and medium enterprises (SMEs) in emerging markets such as Zambia. Generally, the understanding of eCommerce using Web 2.0 social media applications (WSMAs) in SMEs has lacked rigour over time as focus has shifted to pressing issues such as Covid19. This paper purposes to investigate the theoretical foundations and factors influencing WSMA for new eCommerce era in developing countries with particular emphasis on SMEs in Zambia. The methodological research design employs a qualitative study approach using literature reviews, coupled with content analysis of purposively selected articles. Results show that theories such as TAM, TPB, UTAUT2, TOE, TTF, DIT, among others, have guided eCommerce research in SWMA. Behavioural, technological and organisational factors such as trust, ease of use, after-sales logistics, price flexibility have been prevalent, among others. The paper ends with recommendations and strategies for continued adoption of WSMA by SMEs with similar geographical contexts to Zambian context.

**Keywords:** web 2.0 eCommerce, SMEs, developing countries, theories, factors
