The study’s primary goal is to investigate the relationship between different aspects of mindfulness which were carved out by a systematic literature review on sustainability through possible mediators. The relationship between different aspects of mindfulness (acceptance, acting with awareness, decentering, inner awareness, outer awareness, insight) and sustainable attitudes and behavior under the consideration of mediating variables (congruence of attitudes and behavior, values, well-being, connectedness to nature, disruption of routines, pro-socialness) was investigated in 337 participants. The results showed the diverse relation of mindfulness to sustainable attitude and behavior. In a mediation model, sustainable attitude and sustainable behavior were positively predicted by outer awareness and insight via connectedness to nature. Moreover, sustainable attitude and behavior were positively predicted by inner awareness, outer awareness, and insight via pro-socialness. There were no direct effects from any other aspect of mindfulness on sustainable attitude or behavior. Our study hints that connectedness to nature and pro-socialness are the relevant mediators between mindfulness (awareness and insight) and sustainable attitude and behavior. However, further intervention studies should test whether these mindfulness aspects are the most important for changing sustainable attitudes and behaviors.