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. [Correction added on 09 August 2021, after first online publication: The fifth sentence has been updated with more details of the mentors.]