The present study aimed to investigate alexithymia and psychopathological manifestations centered on the body in a sample of adolescents with somatizing and/or self-harming issues to analyze the phenomenon of NSSI linked to Somatic Symptom Disorders (SSD). A sample of 184 adolescents between 12 and 19 years of age, was divided into three groups, one with NSSI (n = 49) and the second group with SSD (n = 57), comparing them with a third group of adolescents with SSD and NSSI (n = 78) to investigate their differences and similarities in psychopathological correlates and to analyze the mediation role of alexithymia and emotional dysregulation in NSSI and SSD related to internalizing problems. The battery of tests included the Toronto Alexithymia Scale (TAS-20) and the Youth Self-Report 11–18 (YSR). The NSSI + SSD group scored higher than the other two groups on all the YSR scales. The affective syndromes were the only clinical condition that discriminated between the three groups. On all the other syndrome scales, the NSSI + SSD group differed from the other two groups, while there were no differences between the NSSI group and the SSD group. The NSSI + SSD group revealed a more severely deficient emotional self-regulation. Difficulty identifying feelings was a trait shared by adolescents with SSD and those engaging in NSSI, a more complex overall alexithymia profile was associated with the combination of self-harming behavior and somatization. Alexithymia and emotional dysregulation played a mediating role in the relationship between internalizing problems and somatization. We did not find a mediating role in alexithymia and emotional dysregulation in the relationship between internalizing problems and self-injurious behavior. The combination of NSSI and SSD gave rise to more severe psychopathological correlates, clinical levels of alexithymia, and more severe deficient emotional self-regulation. Results of mediation role indicated a link between alexithymia, emotional dysregulation, and somatization.