Sustainable solid waste management is a global concern. An effective measure to improve the waste management levels and convert household solid waste into useful materials is to conduct source separation instead of just collecting and burning or burying it. This study adopted a descriptive survey design to determine the current household solid waste source separation practices and how they contribute towards sustainable solid waste management in Kisumu City of Kisumu County, Kenya. Primary data was collected through questionnaires, structured interviews and checklists, while secondary data was acquired through a document review of relevant literature. The data was descriptively analysed on SPSS program. The study found that 80 percent of the respondents believed that household waste separation was possible (mean = 1.26; standard deviation = 0.439). About 62 percent of respondents practiced waste separation before disposal, particularly for food waste, recyclables, and plastics (mean = 2.72; standard deviation = 1.387). About 96 in every 100 respondents believed that separation of household solid waste could enhance hygiene at home (mean = 1.04; standard deviation = 0.202). A significant note was that about 70 percent of the respondents indicated attempting to sensitize their household members on the importance of separation of household solid wastes (mean = 1.30; standard deviation = 0.458). The study recommends the development and implementation of comprehensive public awareness and education initiatives to promote residents' household solid waste source separation behaviour. Such a practice would positively impact on the environment and bring along with it economic advantages of income generation through sale of recyclable materials.