BACKGROUND: While families headed by same-sex couples have achieved greater public visibility in recent years, there are still many challenges for these families in dealing with legal and community contexts that are not supportive of same-sex relationships. The Work, Love, Play study is a large longitudinal study of same-sex parents. It aims to investigate many facets of family life among this sample and examine how they change over time. The study focuses specifically on two key areas missing from the current literature: factors supporting resilience in same-sex parented families; and health and wellbeing outcomes for same-sex couples who undergo separation, including the negotiation of shared parenting arrangements post-separation. The current paper aims to provide a comprehensive overview of the design and methods of this longitudinal study and discuss its significance. METHODS/DESIGN: The Work, Love, Play study is a mixed design, three wave, longitudinal cohort study of same-sex attracted parents. The sample includes lesbian, gay, bisexual and transgender parents in Australia and New Zealand (including single parents within these categories) caring for any children under the age of 18 years. The study will be conducted over six years from 2008 to 2014. Quantitative data are to be collected via three on-line surveys in 2008, 2010 and 2012 from the cohort of parents recruited in Wave1. Qualitative data will be collected via interviews with purposively selected subsamples in 2012 and 2013. Data collection began in 2008 and 355 respondents to Wave One of the study have agreed to participate in future surveys. Work is currently underway to increase this sample size. The methods and survey instruments are described. DISCUSSION: This study will make an important contribution to the existing research on same-sex parented families. Strengths of the study design include the longitudinal method, which will allow understanding of changes over time within internal family relationships and social supports. Further, the mixed method design enables triangulation of qualitative and quantitative data. A broad recruitment strategy has already enabled a large sample size with the inclusion of both gay men and lesbians.