The main objective of this book is to show that neurolinguistic programming, as a mental training that favors the transformation of negative thoughts into positive ones, is a lever for the personal development of ex-inmates. We started from the observation that ex-inmates who were adolescents at the time of their first incarceration and young adults today, experience serious difficulties in their personal development, despite having regained their freedom. Guindon's (1970) theory of the stages of rehabilitation of young offenders states that after undergoing rehabilitation in prison, adolescent ex-offenders are expected to reintegrate harmoniously into society during young adulthood, which is considered the age of crisis resolution. Moreover, a study conducted by Djakba and Makadji (2020) reports that 80% of these ex-prisoners are reincarcerated one year after their release. Thus, in order to boost their developmental level, we conducted an experimental study based on NLP training for young adult ex-prisoners in the Maroua Central Prison.