Abstract The objective of this study was to describe the health status of people living in the slums of Nairobi. It was designed as a cross-sectional study based on data from visitors at a clinic at Trnava University located in Mukuru slum in Nairobi. There were about 16,000 visits registered at Mary Immaculate Clinic of Trnava University in Nairobi during 2 years of operation. A random 5% sample was drawn from the paper-card database of this clinic to assess basic characteristics and health complaints of visitors. Both self-reported health complaints and diagnoses written by physicians were used to assess health status of participants. More females with average age (by slum) ranging from 20.46 to 21.30 years than males with average age ranging from (by slum) 15.86 to 19.49 years are the visitors of the clinic. The major self-reported health complaints of visitors were cough, abdominal pain, and headache for both sexes. The most frequent diagnoses were consequently virosis, acute respiratory infections, and bronchitis. Differences in health complaints by slums were observed and are described herein. The major health complaints and diagnoses in addition to the differences in health complaints and diagnoses by slum show that environmental conditions can have major influences on health status. Therefore, environmental improvements are important in the improvement of health status. A very high prevalence of respiratory complaints and gastrointestinal problems signify that improvements in air pollution reduction, drinking water provision, and waste management in slums can lead to more significant and sustainable improvements in health status than just simple treatment. This fact should be taken into account when planning future relief programs.