Neurofeedback (NF) has emerged as a promising avenue for demonstrating process-related neuroplasticity, enabling self-regulation of brain function. NF targeting the amygdala has drawn attention for therapeutic potential in psychiatry, by potentially harnessing emotion-regulation processes. However, not all individuals respond equally to NF training, possibly due to varying self-regulation abilities. This underscores the importance of understanding the mechanisms behind successful neuromodulation (i.e. capacity). This study aimed to investigate the establishment and neural correlates of neuromodulation capacity by using data from repeated sessions of Amygdala Electrical Finger Print (EFP)-NF and post-training fMRI-NF session.Results from 97 psychiatric patients and healthy participants revealed increased amygdala-EFP neuromodulation capacity over training, associated with post-training amygdala fMRI modulation-capacity and improvements in alexithymia. Individual differences in this capacity were associated with pre-training amygdala reactivity and initial neuromodulation success. Additionally, amygdala down-regulation during fMRI-NF co-modulated with other regions such as the posterior-insula and parahippocampal gyrus. This combined modulation better explained EFP-modulation capacity and improvement in alexithymia than the amygdala modulation alone, suggesting the relevance of this broader network to the gained capacity. These findings support a network-based approach for NF and highlight the need to consider individual differences in brain function and modulation capacity to optimize NF interventions.