The Montreal Neighbourhood Networks and Healthy Aging study was established: (i) to assess the added value in using formal network methods and instruments to measure social capital and its relationship to health; (ii) to determine whether older adults are more vulnerable to the effects of network and neighbourhood environments; and (iii) to examine longitudinally the relationship between social capital and health among adults in Montreal, Canada. The MoNNET-HA cohort consists of men and women aged 25 years and older, residing in the Montreal Metropolitan Area (MMA). Participants were recruited using a random stratified cluster sampling design with oversampling of adults older than 65 years. Initial MoNNET-HA study participants (n1/42707) were recruited for telephone interviews in the summer of 2008. Since 2008, participants were interviewed in the autumn of 2010 and the winter of 2013/2014. Data currently fall into five categories: (i) social network and social capital; (ii) psychosocial and psychological; (ii) socio-demographic and socioeconomic; (iv) health behaviours and conditions; and (v) neighbourhood environmental characteristics. Healthcare utilization data will be available for a subsample of participants. Upon funding, future work will measure anthropometric and metabolic health directly. Based on agreements with participants, external researchers should request access to data via collaborations with the study group.