The field of positive psychology has identified brief interventions that increase individuals' well-being and decrease depressive symptoms. An example is the best possible self (BPS) activity. It is a writing exercise that asks participants to project themselves into the future, and imagine they have met all their goals in every domain of their life. The first objective of this study was to examine the effectiveness of BPS in increasing subjective well-being of youths in an Asian context. 191 participants were recruited from an institute of higher learning in Singapore. Classes were randomly assigned to either the experimental or control group. The experimental group was given instructions for the BPS intervention while the control group was asked to write about their past week. Participants completed two sessions that were 1 month apart. Results indicated that for the first session, the experimental group exhibited a significantly larger decrease in negative affect compared to the control group. Analyses of change scores indicated that changes in positive affect were related to changes in optimism scores whereas changes in negative affect were related to changes in life satisfaction and depressive symptoms. Implications of the findings are discussed.