Objective: The study explores how newly diagnosed patients with acute leukaemia and their patient ambassadors experience the mentorship during the patient ambassador support programme. Methods: Explorative semi-structured individual interviews (n = 28) were carried out in patients with acute leukaemia (n = 15) and their patient ambassadors (n = 13). Interpretive description was the methodological framework used for the thematic analysis of the qualitative interview data. Results: Identified themes were as follows: (a) exchanging life experiences (subthemes: individualised support and a meaningful return); (b) existential cohesion; (c) interreflection; and (d) terms and conditions (subtheme: break in journey). Patients experienced a feeling of being understood, the cohesion leading to hope and a feeling of being able to cope with their situation. Patient ambassadors experienced a sense of meaningfulness and gratitude for life. Conclusions: Patients and patient ambassadors experienced benefits from the individualised support. Their shared experiences created a connection and mutual mirroring, which led to a sense of hope and gratitude for life. Initiatives that introduce peer-to-peer support in newly diagnosed patients with acute leukaemia as part of treatment and in daily clinical practice are crucial. Future studies should further examine the feasibility of peer-to-peer support interventions along the trajectory of acute leukaemia.