This study aimed to explore Swedish mothers’ beliefs about youth well-being and in relation to gender, education, and relationship characteristics. Both qualitative and quantitative approaches were used to study reports provided by 1074 mothers based on open-ended survey questions and mother–youth relationship measures. Fourteen sub-themes were identified that encompassed five broader themes: academic and cognitive, emotional and psychological, physical, recreational, and social well-being. Theme combinations were also identified from individual reports. Although mothers’ beliefs were not moderated by youths’ gender, mothers with higher formal education reported more broadly across themes than mothers with less formal education. No significant differences were observed between mothers’ beliefs and mother–youth relationship characteristics. Situated within a Swedish context, these results lift mothers’ view about youth well-being as a multifaceted phenomenon, including similarities and differences with contemporary theories and studies. Future research needs to explore how these beliefs matter for parents, youth and their well-being across cultures.