Abstract Background Handwashing with soap is critical for the prevention of diarrhoeal diseases and outbreak related diseases, including interrupting the transmission of COVID-19. People living in large displacement settings are particularly vulnerable to such outbreaks, however, practicing handwashing is typically challenging in these contexts. Methods We conducted a qualitative assessment of the implementation of a combined intervention to facilitate handwashing behaviour in displacement camps and in surrounding communities in Bangladesh, Ethiopia and the Democratic Republic of Congo during the COVID-19 pandemic. The intervention comprised a ‘hardware’ infrastructural component (provision of the Oxfam Handwashing Station) and a ‘software’ hygiene promotion package (Mum’s Magic Hands). We used programmatic logbooks, interviews with implementation staff and focus group discussions with crisis-affected populations to assess the use, feasibility and acceptability of the intervention. Results Both components of the intervention were viewed as novel and appealing by implementing staff and crisis-affected populations across the study sites. The acceptability of the handwashing station could be improved by redesigning the tap and legs, exploring local supply chain options, and by providing a greater number of facilities. The implementation of the hygiene promotion package varied substantially by country making it challenging to evaluate and compare. A greater focus on community engagement could address misconceptions, barriers related to the intuitiveness of the handwashing station design, and willingness to participate in the hygiene promotion component. Conclusions The combination of a ‘hardware’ and ‘software’ intervention in these settings appeared to facilitate both access and use of handwashing facilities. The acceptability of the combined intervention was partially because a great deal of effort had been put into their design. However, even when delivering well-designed interventions, there are many contextual aspects that need to be considered, as well as unintended consequences which can affect the acceptability of an intervention.