BACKGROUND: Syrian healthcare workers (HCWs) are among those who fled the Syrian conflict only to face further social and economic challenges in host countries. In Lebanon, this population group cannot formally practice, yet many are believed to be operating informally. These activities remain poorly documented and misunderstood by the academic, policy and humanitarian communities. This study aims to understand mechanisms of informal provision of services, the facilitators and barriers for such practices and to present policy recommendations for building on this adaptive mechanism. METHOD: A qualitative descriptive study based on an in-depth interview approach with a sample of Syrian informal healthcare workers (IHCWs) residing in Lebanon was adopted. Known sponsor networks followed by snowball sampling approaches were used to recruit participants. Data collection occurred between September and December 2017. All interviews were audio-recorded, transcribed and translated into English. An inductive thematic analysis was used. RESULTS: Twenty-two participants were recruited. Motivational factors that led HCWs to practice informally were personal (e.g. source of income/livelihood), societal (cultural competency), and need to fulfill a gap in the formal health service sector. Being connected to a network of IHCWs facilitated initiation of the informal practice until eventually becoming part of a community of informal practice. The central challenge was the informal nature of their practice and its negative consequences. Most IHCWs were afraid of arrest by the government upon identification. Most interviewees indicated being discriminated against by host communities in the form of differential wages and tense interpersonal relationships. Almost all recommended a change in policy allowing them to practice formally under a temporary registration until their return to Syria. CONCLUSION: Our study confirmed the presence of IHCWs operating in Lebanon. Despite its informal nature, participants perceived that this practice was filling a gap in the formal health system and was helping to alleviate the burden of IHCWs and refugee health needs. In line with interviewees' views, we recommend that policy decision makers within humanitarian agencies and the Government of Lebanon explore the possibilities for allowing temporary registration of displaced Syrian IHCW to benefit local host communities and refugee populations.