Loneliness is common among older persons and is associated with adverse health and wellbeing outcomes. We investigated a theory-based intervention that addresses barriers to social contacts and aims at increasing social self-efficacy. Individuals that met pre-assessment criteria of cognitive function, physical health, and loneliness levels were randomly assigned either to the I-SOCIAL intervention that combined both individual and group sessions to address individuals' unique social challenges, or to the control group. Assessment was administered at baseline, after the completion of the intervention, and after a 3-month follow-up period. The intervention group showed significant decline in loneliness level compared to the control group, both after the intervention and after the follow-up period. This innovative combination of analysis of personal barriers, support provided by the counselors, group activities, and individualized suggestions for social activities in the participant's neighborhood, may account for the success of the intervention in decreasing participants' loneliness levels.