OBJECTIVES: Supporting small and nutritionally at-risk (potentially malnourished) infants under six months is a global health priority, albeit with a weak evidence-base. To inform policy and research in this area, we aimed to assess the perceptions and understanding of infant malnutrition and its management among carers, communities, and healthcare workers in rural Ethiopia. METHODS: We conducted in-depth and key-informant interviews, from May-August 2020 in Jimma Zone and Deder District, Ethiopia. We used purposive sampling to recruit the participants. Interviews were transcribed into Amharic or Afaan Oromo and then translated into English. Atlas ti-7 was used to support data analysis. Findings were narrated based on the different themes arising from the interviews. RESULTS: Carers/community members and healthcare workers reported on five different themes: 1) Perceptions about health and well-being: an 'ideal infant' slept well, fed well, was active and looked 'fat'; 2)Perceptions of feeding: overall knowledge of key recommendations like exclusive breastfeeding was good but practices were suboptimal, notably a cultural practice to give water to young infants; 3)Awareness about malnutrition: a key limitation was knowledge of exactly how to identify small and nutritionally at-risk infants; 4) Reasons for malnutrition: levels of understanding varied and included feeding problems and caregiver's work pressures resulting in the premature introduction of complementary feeds; 5) Perceptions about identification & treatment: carers prefer treatment close to home but were concerned about the quality of community-based services. CONCLUSION: To succeed, research projects that investigate programes that manage small and nutritionally at-risk infants under six months should understand and be responsive to the culture and context in which they operate. They should build on community strengths and tackle misunderstandings and barriers. Interventions beyond just focusing on knowledge and attitude of the carers and health workers are necessary to tackle the challenges around infants under 6 months of age at risk of malnutrition. Moreover, stakeholders beyond the health sector should also be involved in order to support the infants under 6 months and their mothers as some of the key reasons behind the at-risk infants are just beyond the capacity of the health sector or health system. Our list of themes could be used to inform infant nutrition work not just in Ethiopia but also in many others.