["Business Strategy and the Environment, Volume 35, Issue 3, Page 4495-4509, March 2026. ", "\nABSTRACT\nFirms face growing pressure to improve environmental performance, yet the psychological traits of CEOs remain an underexplored driver of sustainability outcomes. Building on paradox theory, this study investigates how the coexistence of humility and narcissism in CEOs shapes the environmental performance of European manufacturing firms. Using survey data from 201 managers and applying fuzzy‐set qualitative comparative analysis (fsQCA), we identify the conditions leading to high levels of environmental performance. Results show that outcomes improve when narcissistic ambition is balanced by humility, supported by coherent strategic direction and the active contribution of top management. By contrast, insufficient managerial commitment and limited adaptability to environmental dynamism hinder performance. These findings extend the paradox theory by highlighting how paradoxical traits jointly influence sustainability and demonstrating the value of configurational methods for examining complex causal mechanisms in corporate sustainability.\n"]