Plant leaf functional traits are often used as key traits to characterise plant resource utilisation and ecosystem function. This study investigated the variation in leaf functional traits of urban greening trees and their environmental drivers, focusing on 62 plots and 9 common tree species within Shanghai Outer-Ring Ecological Park Belt. By measuring 9 plant leaf functional traits (leaf area, leaf shape index, leaf dry matter content, specific leaf area, leaf carbon content, leaf nitrogen content, leaf phosphorus content, leaf potassium content) and obtaining atmospheric pollutant concentrations (PM_2.5, O₃, VOCs, NO_x) and soil nutrient content (total nitrogen content, total phosphorus content, total potassium content, ammonium nitrogen content, nitrate nitrogen content, available phosphorus content, available potassium content), the analysis examined responses of these traits to atmospheric pollutants and soil nutrients using a linear mixed-effects model, and further assessed the explanatory power and relative contributions of environmental variables to trait variation. The results indicated that: (1) The leaf functional traits of common tree species in Shanghai exhibited significant intraspecific variation and were influenced by different environmental factors. Specifically, leaf carbon content, leaf nitrogen content, leaf phosphorus content, leaf potassium content, leaf area, specific leaf area, leaf dry matter content, and leaf shape index showed significant responses to atmospheric and soil conditions. (2) Among atmospheric pollutants, PM_2.5 showed a negative correlation with leaf carbon content, while O₃ was negatively correlated with leaf nitrogen content but positively correlated with leaf shape index. VOCs exhibited positive correlations with specific leaf area, leaf nitrogen content, and leaf phosphorus content, but negative correlations with leaf carbon content and leaf dry matter content. (3) For soil nutrients, total nitrogen content and total phosphorus content were negatively correlated with leaf potassium content. Total potassium demonstrated positive correlations with leaf potassium content and leaf nitrogen content, while available potassium content was positively correlated with leaf phosphorus content. Ammonium nitrogen content showed negative correlations with leaf carbon content and leaf nitrogen content, whereas nitrate nitrogen content had positive correlations with leaf area and leaf nitrogen content. (4) Soil nutrients played a more significant role than atmospheric pollutants in explaining leaf functional trait variation. Environmental variables had a higher explanatory power for leaf nutritional traits compared to leaf morphological traits. In conclusion, effective urban forest management in Shanghai required consideration of heterogeneous environmental impacts on tree leaf traits.