This cross-sectional study explored the associations between intrapersonal and interpersonal emotional competence (EC) and the unmet supportive care needs (SCN), anxiety, and depression of informal caregivers at the beginning of gastrointestinal or haematological cancer care, i.e. during chemotherapy and within 6months after diagnosis. The participants completed a self-reported questionnaire, comprising the Short Profile of Emotional Competence (S-PEC), the SCN survey for partners and caregivers (SCNS-P&C), and the Hospital Anxiety and Depression Scale (HADS). Multivariate logistic regression models were performed to explore the influence of EC on unmet SCN and the presence of moderate/severe anxiety or depression. Most of the 203 caregivers were women (n = 141, 69.80%) and the partners of patients (n = 148, 73.27%) suffering from gastrointestinal (n = 112, 55.17%) and haematological (n = 91, 44.83%) cancer. Only intrapersonal EC showed a significant influence out of all the dimensions of unmet SCN related to healthcare services and information (odds ratio (OR) = 0.35 [95%CI 0.19; 0.65]), emotional and psychological needs (OR = 0.43 [95%CI 0.25; 0.74]), work and social security (OR = 0.57 [95%CI 0.37; 0.88]), and communication and family support (OR = 0.61 [95%CI 0.39; 0.95]). A one-unit increase in the intrapersonal EC score significantly reduced the probability of anxiety (OR = 0.42, [95%CI 0.26; 0.68]) and depression (OR = 0.34, [95%CI 0.21; 0.55]). Intrapersonal EC of caregivers is crucial to reduce the risk of unmet SCN, anxiety, and depression from the beginning of care. Identifying caregivers with lower intrapersonal EC may be necessary to increase vigilance from healthcare professionals and psychologists.