Despite the well-documented importance of trust in digital healthcare, its domains are not well-understood, preventing theoretically robust instruments for standardised measurements. We identified instruments measuring trust in digital healthcare, explored definitions, associated factors, and outcomes. We systematically reviewed the literature using tailored searches and 49 studies measuring trust in digital healthcare from either consumers', healthcare professionals', or both perspectives were included. Trust in digital healthcare is complex and, from a consumers' perspective, can influence digital healthcare use, adoption, acceptance, and usefulness. Consumers' trust can be affected by the degree of human interaction in automated interventions, perceived risks, privacy concerns, data accuracy, digital literacy, quality of the digital healthcare intervention, satisfaction, education, and income. Healthcare professionals' trust is enhanced by education and observing good digital health performance. While studies can benefit from rigorous trust measurements, future efforts should address the need for a theoretical framework for trust in digital healthcare.