1. Urbanisation is one of the most significant contributors to the Anthropocene, and urban evolutionary ecology has become an important field of research. While it is commonly assumed that cities impose new and/or stronger selection, the contradictory assertion that selection may be relaxed in cities is also frequently mentioned, and overall our understanding of the effects of urbanisation on natural selection is incomplete. 2. In this review, we first conduct a literature search to find evidence for patterns of natural selection on phenotypic traits including morphology, physiology, behaviour and life history, in urban populations of animals and plants. This search reveals that coefficients of natural selection in the context of urbanisation are scarce (n = 8 studies providing selection gradients/differentials that include a total of n = 200 coefficients) and a lack of standardized methods hinders quantitative comparisons across studies (e.g., with meta-analysis). These studies, however, provide interesting insight on the agents shaping natural selection in cities and improve our mechanistic understanding of selection processes at different spatial scales. 3. We then perform a second literature search to review genomic studies assessing selection intensity in cities on the genome of non-human natural populations. While this search returned 412 articles, only 29 of these truly investigated footprints of selection associated with urbanisation, and only one study provided urban genetic selection coefficients. Here again, we found highly heterogeneous approaches, yet studies provide strong evidence of genomic footprints of urban adaptation. 4. In neither the phenotypic nor genomic literature review were we able to quantitatively assess natural selection across urban versus non-urban habitats. Thus, we propose a roadmap of how future studies should provide standardised metrics to facilitate megaor meta-analyses and explore generalised effects of urbanisation on selection.