While research on grandparenthood has flourished in recent years, few studies have focused specifically on grandfathers. Existing knowledge is informed by uncritical and dated theoretical approaches or based on gender and generational biased data from women and grandchildren. As a result little is known about how men experience being a grandfather and construct their grandfather identities, or how intergenerational relationships influence this, particularly in the contemporary context. To gain more comprehensive knowledge about the influence of intergenerational relations on grandfather identities, 31 in-depths interviews and two participant observations were undertaken in the Lancaster District, UK, with men who are currently grandfathering. A key finding that emerged from the empirical data is that grandfathers perform a variety of different practices in various spaces and this is influenced by the quality and character of intergenerational relationships with both children and grandchildren. Diversity between the men's personal and familial circumstances influences men's involvement with grandchildren and where they grandfather, and consequently how they perform and construct their identities. This suggests that grandfather identities are multi-faceted, heterogeneous and not easily reducible to existing essentialist conceptions of grandfather identities. This thesis further argues that a synthesis of multiple theories of identity construction adopted by human geographers, including practice, performativity and intergenerationality are required to interpret the empirical data, to generate critical understandings of contemporary grandfather identities and the influence of intergenerational relations on these identities; grandfather identities are analysed as practiced and relational identities. This reveals that in order to understand the nature of men's identities as grandfathers and the ways in which they are produced in practice, the effects of their unique intergenerational relations with both grandchildren and children, and their personal and familial contexts need to be understood.