While it has been shown that coffee-shade agroforestry systems require fewer inputs and achieve greater coffee yield stability, little work has focused on the shade tree and environmental processes that control intraspecific leaf trait variation of coffee crops. It has been observed in natural plant communities that functional leaf traits are modified along environmental gradients. Accordingly, we would expect plasticity in coffee leaf traits along a: i) local scale gradient (light and nutrients) induced by shade tree diversity and ii) large scale gradient (climato-edaphic) induced by altitude. The objective of this study was to examine the effect of such environmental gradients on coffee plant response in multiple on-farm research sites of variable shade tree diversity and altitude in the Cartago and San Jose regions of Costa Rica. We analysed coffee under full sun and shade for leaf-level photosynthetic rates (infrared gas analysis), leaf traits (morphological/nutritional) and light transmittance (hemispherical photographs) above coffee strata. Our results show large variability of coffee leaf traits, coffee photosynthetic rates, specific leaf area (SLA) and leaf dry mass deviated with shade tree richness and climato-edaphic conditions. Mean leaf mass and SLA tended to increase with increasing shade tree diversity, with maximal net photosynthesis at 60% total light transmittance under shade canopies. This positive shade tree effect was minimized with increasing altitude where full sun coffee photosynthesized at higher rates than shaded coffee at high altitudes. Concurrently, other coffee leaf traits strongly differentiated between full sun and shaded agroforestry with increasing altitude. Results suggest greater plasticity toward leaf-level resource acquiring traits as shade tree diversity increases, but only in nutrient and climate-limiting environments. These findings help predict coffee performance across environments, whether induced by natural (climato-edaphi