Background: The treatment for retears after arthroscopic rotator cuff repair (ARCR) has long been a challenge. Purpose: This study aimed to (1) summarize the characteristics of patients with a retear after primary ARCR and (2) determine the risk factors for poor clinical outcomes after a retear. Study Design: Case-control study; Level of evidence, 3. Methods: We collected the data of patients with a retear after primary ARCR between January 2011 and December 2016. There were 45 patients with retears included (19 men [42.2%] and 26 women [57.8%]; mean ± SD age, 63.11 ± 8.87 years). Initially, the demographic and outcome data of patients with a retear were analyzed. Patients were classified into good and poor outcome groups according to their overall satisfaction at final follow-up. Univariable and multivariable logistic regression analyses were performed to determine the factors for poor clinical outcomes after a retear. Results: A total of 31 patients were classified into the good outcome group, and 14 patients were classified into the poor outcome group. Both the good and the poor outcome groups showed that clinical scores significantly improved at the time of the retear diagnosis, but the final scores were maintained or worse compared with scores at the time of the retear diagnosis. Final range of motion (ROM), except external rotation in the good outcome group, was worse or had no significant change compared with ROM at the time of the retear diagnosis. On multivariable logistic regression analysis, current smoking (odds ratio [OR], 45.580 [95% CI, 3.014-689.274]; P = .006), female sex (OR, 32.774 [95% CI, 2.433-441.575]; P = .009), and retears of the same or larger size than the initial tear (OR, 10.261 [95% CI, 1.544-68.202]; P = .016) showed a higher OR for poor clinical outcomes after a retear. Conclusion: Smoking, female sex, and retears of the same or larger size than the initial tear were independent risk factors for poor clinical outcomes after a rotator cuff retear. Final clinical scores and ROM were similar or worse compared with the scores and ROM at the time of the retear diagnosis. Therefore, revision surgery should be actively considered in female patients or those who smoke with poor clinical outcomes and a larger retear size than the preoperative tear size at the time of the retear diagnosis.