Background Part-solid lung adenocarcinoma appears as a heterogeneous subgroup, and its surgical management is controversial. This study aimed to elucidate whether preoperative carcinoembryonic antigen, a time-honored tumor marker, can be used as a prognostic factor that contributes to its management. Methods We retrospectively reviewed consecutive patients with clinical-T1a-cN0M0 part-solid adenocarcinoma who underwent surgical resection between January 2011 and December 2015 at two institutions. Results Overall, 288 patients were identified. The median age was 69 years with 176 patients (61%) being female. The median follow-up time was 5.6 years. Lymph node metastases were found in 6 (15%) of 41 patients with elevated carcinoembryonic antigen levels, while 10 (4.0%) of 247 patients had normal carcinoembryonic antigen levels ( P = 0.016). The 5-year overall survival rates in patients with normal and elevated carcinoembryonic antigen levels were 96.9% and 87.2%, respectively ( P = 0.006), and the 5-year relapse-free survival rates were 91.8% and 62.8%, respectively ( P < 0.001). The multivariable analysis revealed that preoperative carcinoembryonic antigen level was a significant prognostic factor for relapse-free survival (hazard ratio [HR] = 2.92, 95% confidence interval [CI] = 1.63–5.25, P < 0.001). Among the patients with elevated carcinoembryonic antigen levels, the 5-year overall survival rates in those undergoing lobar resection and segmentectomy were 87.0% and 88.9%, respectively ( P = 0.59), and the 5-year relapse-free survival rates were 61.7% and 66.7%, respectively ( P = 0.84). Conclusions Our data suggest that preoperative carcinoembryonic antigen level appears to be an important predictor of postoperative survival outcomes in early-stage part-solid adenocarcinoma. Further studies are required to optimize management of patients with elevated preoperative carcinoembryonic antigen levels, although segmentectomy appeared acceptable in those patients.