The aim of this doctoral thesis is to examine the impact of eudaimonia wellbeing beliefs – people conception of the nature and experience of wellbeing – on their wellbeing at workplace, on the organizational performance focused on helping others and on specific prosocial behaviours. Three empirical studies were conducted to this end, using different research designs and samples. Study 1 analyses the moderating role of the two dimensions of eudaimonia wellbeing beliefs (contribution-to-others and self-development) in the relationship between surface acting and exhaustion. We use a cross-sectional self-reported design and a sample of 817 front line employees working in 118 health care organizations providing services to people with intellectual disability. Results confirmed the hypotheses, showing that contribution-to-others strengthens the link from surface acting to exhaustion, whereas self-development weakens this relationship. Study 2 propose the mediation of service climate between employee's contribution-to-others wellbeing beliefs and organizational performance focused on the QoL of individuals with intellectual disability. We propose a multilevel mediation design with two informants: a sample of 885 employees, aggregated at organizational level and a sample of 809 family members as service users. The results supported the hypotheses, showing that when employees believe that their own wellbeing depends on helping others, service climate reported by employees is stimulated. Service climate in turn was associated with organizational performance focused on QoL of people with intellectual disability, assessed by family members. Study 3 examined the direct links from contribution-to-others and self-development to prosocial spending, as well as the interaction between these beliefs and autonomy in predicting the money given. It also tests the effect of a first exposure to a prosocial donation decision on subsequent prosocial spending. We propose an experimental design, using a sample of 200 participants. Results confirmed the existence of a positive significant relationship between contribution-to-others beliefs and prosocial spending, and a significant role of exposure, anchoring, autonomy in predicting the money spent to help vulnerable people. It also shows a significant interaction between autonomy and self-development well-being beliefs, such that autonomy strengthens the link from self-development beliefs to prosocial spending. In general, this doctoral thesis widens the understanding of eudaimonia wellbeing beliefs and their implications on experience wellbeing and helping others in need, both at organizational level, by enhancing the quality of life of service users, and as a citizen by donating to non-profit associations. It also offers a richer portrait of wellbeing, organizational performance and prosocial behavior by integrating different literatures and by considering cross-level, multi-level and experimental approaches.The aim of this doctoral thesis is to examine the impact of eudaimonia wellbeing beliefs – people conception of the nature and experience of wellbeing – on their wellbeing at workplace, on the organizational performance focused on helping others and on specific prosocial behaviours. Three empirical studies were conducted to this end, using different research designs and samples. Study 1 analyses the moderating role of the two dimensions of eudaimonia wellbeing beliefs (contribution-to-others and self-development) in the relationship between surface acting and exhaustion. We use a cross-sectional self-reported design and a sample of 817 front line employees working in 118 health care organizations providing services to people with intellectual disability. Results confirmed the hypotheses, showing that contribution-to-others strengthens the link from surface acting to exhaustion, whereas self-development weakens this relationship. Study 2 propose the mediation of service climate between employee's contribution-to-others wellbeing beliefs and organizational performance focused on the QoL of individuals with intellectual disability. We propose a multilevel mediation design with two informants: a sample of 885 employees, aggregated at organizational level and a sample of 809 family members as service users. The results supported the hypotheses, showing that when employees believe that their own wellbeing depends on helping others, service climate reported by employees is stimulated. Service climate in turn was associated with organizational performance focused on QoL of people with intellectual disability, assessed by family members. Study 3 examined the direct links from contribution-to-others and self-development to prosocial spending, as well as the interaction between these beliefs and autonomy in predicting the money given. It also tests the effect of a first exposure to a prosocial donation decision on subsequent prosocial spending. We propose an experimental design, using a sample of 200 participants. Results confirmed the existence of a positive significant relationship between contribution-to-others beliefs and prosocial spending, and a significant role of exposure, anchoring, autonomy in predicting the money spent to help vulnerable people. It also shows a significant interaction between autonomy and self-development well-being beliefs, such that autonomy strengthens the link from self-development beliefs to prosocial spending. In general, this doctoral thesis widens the understanding of eudaimonia wellbeing beliefs and their implications on experience wellbeing and helping others in need, both at organizational level, by enhancing the quality of life of service users, and as a citizen by donating to non-profit associations. It also offers a richer portrait of wellbeing, organizational performance and prosocial behavior by integrating different literatures and by considering cross-level, multi-level and experimental approaches.