Sufficiency (i.e. adequacy, enoughness) is a sustainability strategy aiming for (1) a decrease in absolute resource consumption on individual and societal levels and (2) for social and ecological justice and the fair distribution of costs and benefits of resource use to meet every human’s basic needs. This study aimed at examining a longitudinal intervention to foster sufficiency orientation at the individual level. We recruited N=252 participants who participated in a one-week reflective diary-intervention to increase sufficiency orientation in every-day life and assessed sufficiency orientation, basic psychological need satisfaction, self-reflection, subjective well-being, and time affluence before (T1), directly after (T2), and four weeks after the intervention (T3). Contrary to our predictions, there was no significant difference between the experimental and the control group. Nevertheless, people with higher basic psychological need satisfaction and subjective well-being reported higher sufficiency orientation. Given the positive relation of basic psychological need satisfaction and sufficiency orientation, targeting basic psychological need satisfaction as an underlying driver seems to be a promising avenue for designing effective interventions. Employing a needs-based, humanistic approach to design psychological interventions is in line with the aims of sufficiency to meet every human’s basic needs, in a both socially and ecologically just world.