Objectives The effects of a range of types of social integration and patterns of change in social integration over time were examined directly in relation to depressive symptoms in a large sample of the Korean population aged ≥45 years. Methods Data from the Korean Longitudinal Study of Aging (KLoSA) between 2006 and 2012 were assessed using longitudinal data analysis. We included 10242 research subjects at baseline (2006) and based the primary analysis on generalised linear mixed models to examine association between social integration and depressive symptom. Results The odds ratio (OR) for depressive symptoms in individuals at the lowest level of social integration was 1.539-fold higher (95% confidence interval (CI) 1.360-1.742) that that for those at highest level of social integration. Results of subgroup analysis according to gender revealed a similar trend. A five-class linear solution fit the data best; Class 1 (lowest constant social integration level, 10.5% of the sample) was significantly associated with the highest risk of depressive symptoms (OR 1.933, 95% CI 1.706-2.190). Conclusions The results of the present study provide a scientific basis for the specific association between the level of social integration and changes in social integration pattern with the risk of depressive symptoms in current practice. Therefore, interventions to provide emotional support for older adults via social integration may be important to protect against depressive symptoms. What is known about the topic? Although there has been considerable discussion about social integration among old adults, few studies related to effect of social integration on depression have been conducted. What does this paper add? The findings of the present study indicate that a high level of social integration is inversely related to depressive symptoms and is also associated with a substantial positive effect on depressive symptoms among individuals aged ≥45 years. What are the implications for practitioners? This paper provides evidence showing that it is useful to assess indicators of both social and emotional loneliness, which have been theorised to correspond to low social integration.