We used a randomized controlled trial to test the effectiveness of a gratitude 3-blessings treatment for enhancing subjective well-being. Although several experimental studies have investigated gratitude interventions, many of these have used inadequate control conditions, and currently we know little about how gratitude treatments work. In this study, subjects were randomly assigned to one of three daily 1-week treatments: memory placebo, pride 3-blessings, or gratitude 3blessings. The gratitude 3-blessings treatment significantly outperformed the comparison treatments in enhancing wellbeing. Moreover, the well-being of those in the gratitude treatment continued to climb after the treatment phase, similar to the findings of Seligman, Steen, Park, and Peterson (2005). We also found that the gratitude treatment enhanced the accessibility of positive memories compared to the comparison treatments. Our results suggest that exercises like the gratitude 3-blessings treatment may train cognitive biases that are salubrious to subjective well-being.