Biodiversity declines are accelerating globally, impacting ecosystem functioning, with consequences for human health. Interactions with biodiversity can be associated with human well-being benefits at the individual level, leading to substantial gains for society when scaled up across populations. However, existing research has not accounted for the species within ecological communities and their effect traits (for example, colours, sounds) that can elicit well-being responses. Many species’ effect traits are seasonal, and spatial variation in exposure to ecosystems by different sectors of society can lead to unequal opportunities to gain well-being. Here we use an interdisciplinary analytical approach to explore how the association between forest biodiversity and well-being fluctuates: (1) temporally, between different seasons and (2) spatially, across socio-economic deprivation gradients at a national scale (England and Wales). Species’ effect traits and participant well-being were derived through a series of seasonal participatory workshops and questionnaires that incorporated BIO-WELL (a biodiversity–well-being psychometric scale). By generating spatially explicit data, we could examine variability in forest biodiversity associated with human well-being across socio-economic deprivation gradients. Forest species’ effect trait richness was spatially heterogeneous, particularly in autumn, spring and summer. Broadleaf forests had greater species’ effect trait richness than other categories of forest. Forests with higher species’ effect trait richness and forests that were associated with higher self-reported participant well-being were in areas with the least socio-economic deprivation. Forest creation/restoration and nature–health interventions must recognize this ecological and social diversity to ensure initiatives are equitable and socially just.