The impact of nine strengths-based positive interventions on well-being and depression was examined in an Internet-based randomized placebo-controlled study. The aims of the study were to: (1) replicate findings on the effectiveness of the gratitude visit, three good things, and using character strengths interventions; (2) test variants of interventions (noting three good things for 2 weeks; combining the gratitude visit and three good things interventions; and noting three funny things for a week); and (3) test the effectiveness of the counting kindness, gift of time, and another door opens-interventions in an online setting. A total of 622 adults subjected themselves to one of the nine interventions or to a placebo control exercise (early memories) and thereafter estimated their degrees of happiness and depression at five times (pre- and post-test, 1-, 3-, and 6 months follow-up). Eight of the nine interventions increased happiness; depression was decreased in all groups, including the placebo control group. We conclude that happiness can be enhanced through some ‘‘strengths-based’’ interventions. Possible mechanisms for the effectiveness of the interventions are discussed.