Abstract: Objective: Attachment styles (secure, preoccupied, dismissing, fearful) of adults has been suggested as having an effect on other aspects of their lives. Defence mechanisms are unconscious psychological processes that help people deal with internal and external stress factors. Research has shown that there is a meaningful relationship between attachment styles and defence mechanisms. Life satisfaction is evaluated subjectively via the standards that people apply to themselves. The purpose of this research is to examine the relationship between adult attachment styles, defence mechanisms and life satisfaction. Method: 336 adults between the ages of 18-65 (28% male – 72% female) voluntarily participated in this study. The data collection tools were; Socio-demographic Data Form, a Relationship Styles Questionnaire, a Defence Style Questionnaire and Satisfaction with Life Scale. SPSS 22.0 (Statistical Package Program for Social Science) for Windows was used for the analysis of the obtained data. In order to detect the distribution of socio-demographic variables, frequency analysis was used. Independent T-Test Analysis and One-Way Variance Analysis (ANOVA) were used to assess relationships between applied scales. Multivariate Analysis of Variance (MANOVA) was used to compare multivariate sample means. The relationship between applied scales was tested by Pearson Correlation. Regression Analysis was used to determine predictive effects of applied scales. Results: Results have shown that 42% that participated in this study were securely attached; while 20% had fearful, 8% had preoccupied, and 30% had dismissing attachment styles. The majority (333 out of 336) in this study were identified as using immature defence mechanisms. While 3 people were identified as using mature defence mechanisms, none were identified as using neurotic defences. The average of the life satisfaction scale was determined to be 23.30. Gender has a statistically significant difference for attachment styles; the average dismissing style points for women are higher than those for men. Age also has a statistically significant difference; the average age of people with preoccupied attachments style is higher than the average age of people with fearful attachment style. The results show that people who use mature defence mechanisms have higher life satisfaction averages than people who use immature defence mechanisms. Conclusion: There is a significant and positive correlation between secure attachment style and life satisfaction while there is a significant and negative correlation between secure attachment style and immature defence mechanisms. Between life satisfaction and mature/neurotic defences there is a significant and positive correlation. Immature defences have negative predictive effects on secure attachment but positive predictive effects on dismissing attachment.