Lifespan integration (LI) is a recent psychotherapy, developed in 2002 by Peggy Pace. Its main focus is to treat trauma and dissociative disorders. Repetitions of the LI time line seem to promote the development of a feeling of integration in the patient, allowing the patient to build a more solid central self. This qualitative study aimed to explore, from the LI therapists’ points of view, the feeling of integration, which results from LI. Fourteen certified or pre-certified LI therapists were recruited within the French-speaking Association of Lifespan Integration. These therapists took part in a semi-structured interview exploring their perceptions and understanding about LI and the feeling of integration. A general inductive approach was chosen to capture therapists’ representations. Results showed that, according to therapists, LI therapy facilitates one’s connection to his/her experience, improves emotional regulation, and increases the general sense of well-being associated with self-acceptance. These changes are related to repetitions of the LI time line and the therapist’s attunement to the patient. In addition, the results indicate that this feeling of integration corresponds to a new state of connection to one’s identity and one’s experience. Therapists in this study reported that repetitions of the LI time line integrated the patient’s history into a continuum, strengthening psychological bases such as safety and individuation, giving meaning to the lived experiences/life story, and increasing self-confidence. This study provides a better understanding of the feeling of integration resulting from LI therapy. Further studies should explore the patients’ experience in LI and try to measure feeling of integration during LI psychotherapy.