According to previous reports, mental well-being is conducive to increased pro-social behavior and achievement in several domains. Previous studies have also indicated that P4C has a positive impact on mental well-being. In this paper, we discuss how philosophical dialogues affect the mental well-being of persons with acquired brain injuries (ABI), a group for which increases in mental and social well-being as well as performance are especially important. The paper is based on a small-scale study carried out by the researchers in the ongoing research project Education for Participation – Philosophizing back a ”new” life after acquired brain injury (funded by the Swedish Research Council). The research group has attempted to assess effects of two single group small-scale interventions (a weak experimental pre-test post-test design with the two experimental groups as control groups before the intervention started) that were made in the northern part of Sweden. The two groups participated in twelve philosophical dialogues each during a period of fifteen weeks from January 2015 to May 2015. In addition to the persons with ABI, staff participated in the philosophical dialogues in both groups. Besides cognition and communication measurements, the research group measured subjective well-being, which is targeted in this paper. Individual in-depth semi-structured interviews were carried out with all of the participants with ABI based on the following two subjective well-being measurements: (i) the Cantril Ladder, and (ii) The Satisfaction With Life Scale. To utilize the Cantril Ladder, we partly adapted it for the study population and translated it to Swedish. We used the recommended non-verbal ladder device ranging from 0–10, where the top was described as the best life, and the bottom the worst life, as the interviewee defined it. Each interviewee was asked questions about how he/she defined the best and the worst possible future life in terms of happiness and unhappiness, where he/she thinks he/she stands on the ladder today, where he/she stood five years ago, where he/she stood before the ABI, and where he/she will stand in the future. The Satisfaction With Life Scale ranges form 1–7 and contains the following five items: 1) ”In most ways my life is close to my ideal.”, 2) ”The conditions of my life are excellent.”, 3) ”I am satisfied with my life.”, 4) ”So far I have gotten the important things I want in life.”, and 5) ”If I could live my life over, I would change almost nothing.”. (We used a Swedish translation of the questions.) The data collection was finished in June 2015. In this paper, we present some preliminary results. In short, the processed data (to date) indicate that the philosophical dialogues were accompanied by an increase in subjective well-being among the participants with ABI, which makes the case stronger for P4C/PWC as an educational method applicable also in special needs education.