This study was performed to compare clinical outcomes of lymphatic n-butyl cyanoacrylate (NBCA) embolization and ethanol sclerotherapy in patients with symptomatic postoperative pelvic lymphoceles. This prospective, open-label, randomized, and controlled trial took place at two medical centers in Korea. Patients ≥ 18 years old with symptomatic postoperative pelvic lymphoceles were randomly assigned (1:1) to one of two study arms: embolization or sclerotherapy. A target of 44 patients was set for each group to assess clinical outcomes. The trial began in August 2018 but ended as a pilot study in February 2020. Problematic patient enrollment precluded full population recruitment, only 11 patients (embolization, 5; sclerotherapy, 6) eventually participating. Clinical success and drainage tube removal rates were 100% in both arms. To achieve clinical success, significantly more procedures were needed in the sclerotherapy group than in the embolization group (4.5 ± 1.23 vs 2.0 ± 1.00; p < 0.001). The time to achieve daily drainage reduction thresholds (< 20 mL or < 20% of initial daily drainage) was also less in the sclerotherapy (vs embolization) group but fell short of statistical significance (4.8 ± 2.63 days vs 7.0 ± 3.67 days; p = 0.267). No significant adverse events or recurring symptomatic lymphoceles were evident at 3-month follow-up visits. Both NBCA embolization and ethanol sclerotherapy might be safe and effective in treating symptomatic postoperative pelvic lymphoceles, showing no significant difference in clinical outcomes. In a future randomized prospective study, it is essential to establish better inclusion criteria to selectively include intractable lymphoceles to find out the difference in the outcome between the two treatments. Trial registration: The study is registered as KCT0003078 at the Clinical Research Information Service ( http://cris.nih.go.kr ). Registered April 2, 2018.