Rapid urbanisation and climate change intensify heat, drought, wind exposure, and salinity risks in arid coastal cities, while simultaneously increasing dependence on trees for microclimate regulation and public-space quality. However, integrated evidence linking taxonomic concentration, spatial structure, tree dimensions, and current vitality remains scarce for Central Asian cities on the Caspian coast. This study characterised 13,951 trees across 10 green spaces in Aktau, Kazakhstan, belonging to 10 species, 10 genera, and 7 families, using a comprehensive inventory and an integrated taxonomic, spatial, and vitality framework. Stand density ranged from 27.1 to 510.3 trees ha−1. Ailanthus altissima and Platycladus orientalis accounted for 42.74% and 23.13% of all trees, respectively, and together formed 65.87% of the inventory. Two species, two genera, and one family exceeded the indicative 10/20/30 diversification thresholds. The Shannon index ranged from 1.19 to 2.00, Pielou evenness from 0.52 to 0.87, and the share of the dominant species from 24.2% to 63.2%. Of all trees, 12,205 (87.48%) were classified as in good condition, but three sites accounted for 83.0% of all satisfactory or unsatisfactory trees. Maclura pomifera and Gleditsia triacanthos had the highest proportions of trees in good condition (96.3% and 94.2%), whereas Catalpa speciosa had the lowest (66.0%). The inventory, therefore, reveals a favourable current condition, but limited taxonomic redundancy and localised management hotspots. The findings provide a baseline for climate-resilient urban landscape planning based on gradual diversification, site-specific irrigation and soil management, control of invasive recruitment, and repeated monitoring of condition, growth, and mortality.