Summary Objectives Recent years have seen renewed interest for the study of motivations underlying the adoption of sexual behavior. And yet, there is still very little investigation into the psychological determinants of sexual motivation. To contribute to this field of knowledge we analyze the relationships between defense mechanisms and sexual motivations. Method Data for 295 subjects were collected online (241 women, 54 men, mean age: 23.26 years). The evaluation of defensive functioning was carried out using the Defense Style Questionnaire in its 28-item version. Sexual motivations were assessed using the French translation of the Reason for Having Sex Questionnaire (YSEX). Main Results Loving and physical motives lead most frequently to sexual relations. Positive correlations were found between mature defense styles and the number of sexual partners. Multiple regression analysis shows that defenses significantly contribute to explaining between 4.3 and 8.6% of variance in sexual motives. Regardless of the defensive style considered, the correlation is positive. Immature defense mechanisms are the main defenses related to sexual motives. Results are discussed according to literature on sexual motives and literature on defense mechanisms. Conclusion Psycho-sexological consultations investigating motivations for sexuality could benefit from a differential approach based on prior assessment of defensive functioning in order to best individually adapt clinical care.