Objective: To develop a theoretically grounded measure of self-perceived ability to cope with stress in a flexible (i.e. non-rigid) manner and test associations with well-being. Method: Participants in Study 1 (N = 395, 17–56 years) completed surveys to report flexible coping with stress and well-being. In Studies 2 (N = 645, 17–27 years) and 3 (N = 558, 12–19 years), youth completed surveys with the 18-item Self-Perception of Flexible Coping with Stress (SFCS), and coping and well-being measures. Results: Three SFCS factors were supported, which aligned to the conceptualization including multiple coping strategy use (multiple CSU), coping rigidity, and situational coping. The SFCS subscales had good reliability and were modestly correlated with each other. Also, multiple CSU and situational coping were linked to better mental health, emotion regulation, greater use of adaptive coping strategies, and better self-worth. Coping rigidity was linked with more symptoms of anxiety and depression, more emotion dysregulation, greater use of problem-coping behaviors, and lower self-worth. Older participants reported they were higher in flexible coping and sex differences in multiple CSU and situational coping were found. Conclusions. The SFCS, a measure of the deployment of a coping “toolbox” that could allow individuals to respond adroitly to stressors, is reliable, valid, and associated with well-being.