Background: Poor adherence is one of the leading problems affecting the effectiveness of treatment in schizophrenia. It is an identified factor for relapse and hospitalizations with major social and economic consequences. Various determinants of poor adherence have been identified but few studies investigate the role of therapeutic alliance on medication adherence in routine mental healthcare. Aims: To investigate links between therapeutic alliance insight and medication adherence in routine care and community psychiatry. Methods: In this cross-sectional study, 38 inpatients that met ICD-10 criteria for schizophrenia or schizoaffective disorder were recruited and independently interviewed just before discharge. Various rating scales were used: the self-reported 4-Point ordinal Alliance Scale (4PAS), the Medication Adherence Rating Scale (MARS) and the Scale to assess Unawareness of Mental Disorder (SUMD). In addition, we investigated the relationships between medication adherence and clinical variables through uni- and multivariate analysis. Results: Therapeutic alliance was significantly correlated with adherence (r = 0.663, P < 0.0001) and insight (r =−0.664, P < 0.0001). Poor adherence was associated in patients with substance or alcohol use disorders (5.4 vs. 2.9, P = 0.0075, t = 2.83). No significant difference was found between the demographic characteristics of the sample, the characteristics of the treatments and adherence. Conclusions: A weak therapeutic alliance and low insight are associated with poor adherence in patients with schizophrenia or schizoaffective disorder who were hospitalized. Specific psycho-educational programs to improve therapeutic alliance and insight should be implemented to achieve better therapeutic adherence and outcome.