Health care complaints are an underutilized resource for quality and safety improvement. Most research on health care complaints is focused on secondary care. However, there is also a need to consider patient safety in general practice, and complaints could inform quality and safety improvement. This review aimed to synthesize the extant research on complaints in general practice. Five electronic databases were searched: Medline, Web of Science, CINAHL, PsycINFO and Academic Search Complete. Peer-reviewed studies describing the content, impact of and motivation for complaints were included and data extracted. Framework synthesis was conducted using the Healthcare Complaints Analysis Tool (HCAT) as an organizing framework. Methodological quality was appraised using the Quality Assessment Tool for Studies with Diverse Designs (QATSDD). The search identified 2960 records, with 21 studies meeting inclusion criteria. Methodological quality was found to be variable. The contents of complaints were classified using the HCAT, with 126 complaints (54%) classified in the Clinical domain, 55 (23%) classified as Management and 54 (23%) classified as Relationships. Motivations identified for making complaints included quality improvement for other patients and monetary compensation. Complaints had both positive and negative impacts on individuals and systems involved. This review highlighted the high proportion of clinical complaints in general practice compared to secondary care, patients' motivations for making complaints and the positive and negative impacts that complaints can have on health care systems. Future research focused on the reliable coding of complaints and their use to improve quality and safety in general practice is required.