Background: Telephone triage is used to facilitate efficient and adequate acute care allocation, for instance in out-of-hours primary care services (OPCSs). Remote assessment of health problems is challenging and could be impeded by a patient's ambiguous formulation of his or her healthcare need. Socioeconomically vulnerable patients may experience more difficulty in expressing their healthcare need. We aimed to assess whether income differences exist in the patient's presented symptoms, assessed urgency and allocation of follow-up care in OPCS. Method: Data were derived from Nivel Primary Care Database encompassing electronic health record data of 1.3 million patients from 28 OPCSs in 2017 in the Netherlands. These were linked to sociodemographic population registry data. Multilevel logistic regression analyses (contacts clustered in patients), adjusted for patient characteristics (eg, age, sex), were conducted to study associations of symptoms, urgency assessment and follow-up care with patients' income (standardised for household size as socioeconomic status (SES) indicator). Results: The most frequently presented symptoms deduced during triage slightly differed across SES groups, with a larger relative share of trauma in the high-income groups. No SES differences were observed in urgency assessment. After triage, low income was associated with a higher probability of receiving telephone advice and home visits, and fewer consultations at the OPCS. Conclusions: SES differences in the patient's presented symptom and in follow-up in OPCS suggest that the underlying health status and the ability to express care needs affect the telephone triage process. Further research should focus on opportunities to better tailor the telephone triage process to socioeconomically vulnerable patients.