Background: Patients with advanced disease experience high levels of psychological distress, yet there is low uptake of psychosocial services offered to patients who screened positive for distress. In this study we aimed to identify predictors for use of psychosocial services in patients with metastatic colorectal cancer (mCRC) receiving first line chemotherapy enrolled in a prospective cluster randomized trial (CRT). Methods: Patients completed measures on psychological distress, physical distress, and quality of life at baseline. Demographics, clinical characteristics at baseline and clinical events during treatment (e.g. severe adverse events, clinical benefit) were extracted from patient records. Patients reported psychosocial service utilization in- and outside the hospital after 10, 24 and 48 weeks of treatment. Multivariable logistic regression models were used to identify predictors for the use of psychosocial services. Results: Out of 349 patients, seventy patients (20.0%) used psychosocial support services during the follow-up period. Use of psychosocial services was associated with younger age, a higher educational level, presence of more pain (at baseline), and the expressed need to talk to a professional (at baseline). In addition, patients without progressive disease within the first ten weeks of treatment were more likely to use psychosocial services. Conclusions: One in five patients with mCRC receiving first line palliative treatment used psychosocial services during this prospective longitudinal CRT. Sociodemographic factors (age, education), clinical factors (pain and no progressive disease) and the expressed need to talk to a professional predicted use of psychosocial services. Identification of these predictors may contribute to the understanding of factors that determine the need for psychosocial services. Trial registration: Netherlands Trial Register NTR4034.