Background: Parent who spent much of their time working outside of the home tend to cause a sense of more loneliness in their children. Therefore there is a serious concern over the harmful effects brought upon the children due to decline in the amount of quantitative and qualitative time parents spent with them. Children who are left alone have poor cognitive development also. So keeping all in this view, the present study aims to correlate the loneliness and cognitive development of latchkey children (age between 10-12 years). Method: Descriptive correlational research design was adopted for this study .A sample of 100 latchkey children was selected by purposive sampling technique from three selected schools of Mangalore A demographic data, Screening questionnaire, UCLA Loneliness scale and Cognitive questionnaire was used for data collection. Result: The result revealed that there is a significant negative relationship between level of loneliness and cognitive development of latchkey children (r = -0.13) at p < 0.05. Result showed that there is a significant association between level of cognitive development of latchkey children ( 10-12) with religion and also found that there was no significant association between the level of loneliness of latchkey children ( 10-12 years ) with age, sex, religion and educational status. Conclusion: The study concluded that latchkey children (age 10-12yeras) feels frequent lonely and have average cognitive development.