Mentoring programmes targeting young people in residential care need to promote long-term mentorships. Youth in residential care are a sensitive population that can be particularly affected by the ending of a mentorship relationship, due to their troubled bonding history. However, little is known about the difficulties mentors may encounter in such programmes, how to help mentors overcome problems, have a good mentoring experience and, ultimately, how to retain mentors. Within the framework of a pilot mentoring program aimed at youth in residential care carried out in five European countries, a two-phase study was designed to (1) explore positive factors and difficulties faced by mentors and (2) analyse the perceived benefits of participating in such a program. This article reports on findings from sixteen interviews with mentors in Spain and a survey of 62 mentors in Austria, Croatia, France, Germany and Spain. Factors that contribute to promoting a better mentoring experience and longer-term mentorships include taking care of the relationship between mentor and youth in residential care, encouraging youth in residential care to participate in decision-making and promoting collaboration between stakeholders. Minimising the impact of negative external factors from different contexts is also important. Finally, a key role is played by reinforcing mentor well-being, personal growth, socialisation and social awareness.