Despite the assumed importance of the residential environment for treatment outcomes, there is a gap in research examining the relation between therapeutic alliance and group climate. Therefore, this prospective study examined the association between positive and negative group climate and child-mentor therapeutic alliance in residential youth care in two mixed gender samples, with two measurement occasions at a six-month interval: N = 43 children (58% boys, 42% girls) in age category 4-8 (M = 6.11 years; SD = 1.19; Min = 4.09; Max = 8.79), and N = 72 children (72% boys, 28% girls) in age category 8-15 (M = 11.48 years; SD = 1.69; Min = 8.31; Max = 14.73). We found moderate six-month stability in children’s ratings of group climate and alliance, although stability was weaker for the 4-8 year olds compared to the 8-15 year olds. In addition, positive group climate was rated higher by boys than girls in the group of 8-15 year olds. No effects were found between group climate and alliance ratings over the two measurement occasions. Implications for practice and future research are discussed. [ABSTRACT FROM AUTHOR]