Breastfeeding is at its best when both the mother and infant benefit from the experience. Aim: To obtain data on the adequacy of the diet and nutrition knowledge of lactating women (0-6 months postpartum) living in a low socio-economic area in Nairobi. The findings could be used to plan future nutrition intervention programs. Research design: A cross-sectional survey in the quantitative and qualitative research paradigms. Health status indicators, socio-economic and cultural factors were additionally investigated as interactive factors that could influence the nutrient intake and nutrition knowledge of the lactating women. Setting: Mbagathi District Hospital, located at the edge of Kibera slum area in Nairobi. Sample: Lactating mothers (0-6 months postpartum), who were visiting the Maternal-Child Health Clinic to bring their children for immunisation, were recruited. Convenience sampling was used (N=120). Informed consent was obtained from the mothers in their home tongue. Methodology: Individual interviews in Swahili, using structured questionnaires (Socio biodemographic questionnaire, Hunger Scale, 24 Hour-recall, and Quantitative Food Frequency Questionnaire), and anthropometry (according to standard procedure) were done in the quantitative domain. Seven structured focus group discussions were employed in the qualitative domain. Descriptive and inferential statistics were used on the quantitative data, and Krueger‘s framework of analysis on the qualitative data. Ethical approval was obtained from the Ethics Committee, Faculty of Natural and Agricultural Sciences, University of Pretoria; Ref no EC 080922-039, and research permission was granted by the National Council for Science and Technology, Nairobi; Permit no NCST/5/002/R/355. Main findings: Majority of women (92%) had energy intakes between 5040 – 10080 kJ/day with the mean energy intake of 6975.5 kJ/day which was lower than the recommended 11340 kJ/day. Macronutrient intake was within the acceptable macronutrient distribution ranges, whereas the micronutrients were consumed below the recommended dietary allowances (WHO). The mean adequacy ratio (excluding niacin) was 0.74. The highest frequency of consumption (100%) was from cereals, while the lowest were for vitamin A rich vegetables/fruits (6.6%) and dairy products (1.7%). Overall, the mean Food Variety Score (FVS) was 6.6 ( ± 2.0) and the Dietary Diversity Score (DDS) was 4.3 ( ± 1.0). Hunger assessment revealed 43 households that were food secure, whereas 77 households were either hungry or at risk of hunger. Majority of women (93%) had good nutrition knowledge but the rationale for applying the knowledge was lacking for most of the nutrition concepts. Socio-economic status, cultural beliefs and practices, health status and nutrition knowledge were all identified as probable factors that influenced the dietary intake of the lactating women. Recommendation: There seems to be a need for well-designed nutrition intervention programs focusing on nutrient intake from culturally acceptable and affordable foods to increase dietary diversity and food variety of lactating women in this low socio-economic area. With a concurrent increase in nutrition knowledge such interventions would improve their nutritional status.