Objective To quantify the different types of health outcomes assessed as primary outcomes in randomized controlled trials (RCTs) in the primary care (PC) setting during the last 20 years and identify whether potential gaps exist in specific types of health care and types of intervention. Methods We systematically searched PubMed, Scopus, and Cochrane Central Register of Controlled Trials, from January 2000 to September 2020 for published RCTs in PC. We recorded characteristics of eligible studies and mapped evidence by health outcome category (patient health outcomes, health services outcomes); and for each outcome category, by types of health care (preventive, acute, chronic, palliative), and by types of intervention (drug, behavioural, on structure, and on process). For RCTs assessing patient health outcomes as primary outcomes, we further mapped using the quality-of-care dimensions, that is, effectiveness, safety, and patient-centredness. Results Of the 518 eligible RCTs in PC, 357 (68.9%) evaluated a patient health outcome as the primary outcome, and 161 (31.1%) evaluated only health services outcomes as primary outcomes. Many focused on population with chronic illness (224 trials; 43.2%) and evaluated interventions on processes of health care (239 trials; 46.1%). Research gaps identified include preventive and palliative care, behavioural interventions, and safety and patient-centredness outcomes as primary outcomes. Conclusion Our evidence map showed research gaps in certain types of health care and interventions. It also showed research gaps in assessing safety and measures to place patient at the centre of health care delivery as primary outcomes.