This study investigated the variance in subjective well-being (SWB) of early adolescents ( n = 54) exposed to a positive psychology intervention aimed at increasing positive affect and life satisfaction as well as decreasing negative affect through intentional activities (e.g., gratitude journals, acts of kindness, use of character strengths, optimistic thinking). Understanding how to increase SWB among youth is important because of its associations with positive indicators of psychological and academic functioning. However, prior research is limited regarding interventions targeting SWB in youth and excludes the relation of common factors of therapeutic change. Based on the literature regarding therapeutic change, youth factors (i.e., parent support, social self-efficacy), therapeutic alliance, and participant expectancy for change were investigated to determine possible relation beyond the effects of intervention. Results of simultaneous multiple regression analyses indicate that specific common factors (i.e., expectancy, child-rated alliance, social self-efficacy), but not the SWB intervention, significantly relate to positive affect; further, data trends indicate the probable relation of positive psychology intervention to life satisfaction. Other data trends and indications for future research are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]