Mental illness among the elderly population is a pressing public health concern that demands attention and understanding. The study is aimed at assessing knowledge and perception of mental illness among the elderly living at Ijora-Oloye community, Apapa, Lagos. Four specific objectives and three hypotheses were formulated to guide the study. A quantitative cross-sectional study design was adopted in this study as the primary data were gotten through administration of questionnaire to selected 80 elderly in Ijora-Oloye, Lagos State, using simple random sampling technique. The data was collected and collated into Microsoft Excel and was analysed using Statistical Package for Social Sciences (SPSS) software version 26. A descriptive analysis is done mainly to assess the description of the data obtained. Inferential statistics using Chi-Square analysis was conducted to determine the hypothesis. This study revealed that participants have excellent knowledge about mental illness as positive perception was observed with (46.3% agree, 28.7% strongly agree) reported that people with mental illness can recover and lead normal lives when they get treatments. Good attitude about mental illness was also observed as (28.7% agree, 15% strongly agree) reported that they would be comfortable talking with someone with a mental illness. This study revealed that there is no significant difference between gender and knowledge of mental illness among elderly individuals based on their exposure to mental health education. This denotes that gender of elderly living has no influence on their knowledge about mental illness. Also, elderly individuals with higher educational level have better knowledge and more positive perceptions of mental illness. Lastly, religion does not affect elderly individuals' knowledge and perceptions of mental illness. The result confirmed that religion of respective elderly individuals’ does not influence their knowledge and perception of mental illness