Limited data suggest that early palliative care (EPC) improves quality of life (QOL) and survival in patients with advanced cancer. To evaluate whether comprehensive EPC improves QOL; relieves mental, social, and existential burdens; increases survival rates; and helps patients develop coping skills. This nonblinded randomized clinical trial (RCT) recruited patients from 12 hospitals in South Korea from September 2017 to October 2018. Patients aged 20 years or older with advanced cancer who were not terminally ill but for whom standard chemotherapy has not been effective were eligible. Participants were randomized 1:1 to the control (receiving usual supportive oncological care) or intervention (receiving EPC with usual oncological care) group. Intention-to-treat data analysis was conducted between September and December 2022. The intervention group received EPC through a structured program of self-study education materials, telephone coaching, and regular assessments by an integrated palliative care team. The primary outcome was the change in overall QOL score (assessed with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 15 Palliative Care) from baseline to 24 weeks after enrollment, with evaluations also conducted at 12 and 18 weeks. Secondary outcomes were social and existential burdens (assessed with the McGill Quality of Life Questionnaire) as well as crisis-overcoming capacity and 2-year survival. A total of 144 patients (83 males [57.6%]; mean [SD] age, 60.7 (7.2) years) were enrolled, of whom 73 were randomized to the intervention group and 71 to the control group. The intervention group demonstrated significantly greater changes in scores in overall health status or QOL from baseline, especially at 18 weeks (11.00 [95% CI, 0.78-21.22] points; P = .04; effect size = 0.42). However, at 12 and 24 weeks, there were no significant differences observed. Compared with the control group, the intervention group also showed significant improvement in self-management or coping skills over 24 weeks (20.51 [95% CI, 12.41-28.61] points; P < .001; effect size = 0.93). While the overall survival rate was higher in the intervention vs control group, the difference was not significant. In the intervention group, however, those who received 10 or more EPC interventions (eg, telephone coaching sessions and care team meetings) showed a significantly increased probability of 2-year survival (53.6%; P < .001). This RCT demonstrated that EPC enhanced QOL at 18 weeks; however, no significant improvements were observed at 12 and 24 weeks. An increased number of interventions sessions was associated with increased 2-year survival rates in the intervention group. ClinicalTrials.gov Identifier: NCT03181854.