Loneliness and cognitive distortions have serious negative effects on life satisfaction and are seen as related to each other. However, what mediates in these relationships has not been adequately analyzed. This study aims to analyze the effect between cognitive distortions and life satisfaction by asserting the mediating role of loneliness. For this purpose, we conducted a cross-sectional study with 978 people over the age of 20 from various parts of Turkey using a general screening model. Firstly, we analyzed the direct effect of interpersonal rejection, interpersonal misperception, and unrealistic relationship expectation, which are sub-dimensions of cognitive distortions, loneliness, and life satisfaction. Secondly, we analyzed the effects of independent, mediation, and interaction (Loneliness X age) variables on satisfaction with life. Thirdly, we applied direct regression analysis between independent, mediating, and dependent variables to conduct the mediation analysis of the study. Also, we examined age as a moderator between loneliness and life satisfaction. The results showed loneliness as an essential determinant between cognitive distortions and life satisfaction. Moreover, in the moderation analysis, we found some age-related differences between loneliness and life satisfaction. According to this, both loneliness and life satisfaction increased with increasing age. However, life satisfaction decreased as loneliness increased in young people. Being able to compensate for loneliness in the aging process is an essential psychological indicator. Although young people have more opportunities than older people, their ability to cope with negative situations such as loneliness is largely undeveloped. These results showed both psychological and sociological problems of loneliness. Therefore, the results can be useful for the prevention of loneliness and the development of intervention programs.