Purpose To provide a comparative 30-day postoperative analysis of complications and unplanned readmission rates, using the National Surgical Quality Improvement Program database, after open or arthroscopic rotator cuff repair (RCR). Methods The American College of Surgeons National Surgical Quality Improvement Program database was reviewed for postoperative complications after open or arthroscopic RCR over an 8-year period, from 2007 through 2014. Patients were identified by use of Current Procedural Terminology codes. The open group contained 3,590 cases (21.8%) and the arthroscopic group had 12,882 cases (78.2%), for a total of 16,472 patients undergoing RCR. The risk of complications was compared between the 2 groups, along with patient demographic characteristics, operative time, length of stay, and unplanned readmission within 30 days. We compared dichotomous variables using the Fisher exact test and continuous variables with 1-way analysis of variance. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated when appropriate. Results The open RCR group had a higher prevalence of patients aged 65 years or older and comorbidities such as hypertension, diabetes, chronic obstructive pulmonary disease, smoking, and alcoholism (P <.05). Patients undergoing open RCR had a higher risk of any adverse event when compared with arthroscopic RCR patients (1.48% vs 0.84%; RR, 1.17; 95% CI, 1.05-1.30; P =.0010). They were also at higher risk of return to the operating room within 30 days (0.70% vs 0.26%; RR, 1.36; 95% CI, 1.09-1.69; P =.0004). Open RCR was associated with a longer average hospital stay (0.48 ± 2.7 days vs 0.23 ± 4.2 days, P =.0007), whereas arthroscopic RCR had a longer average operative time (90 ± 45 minutes vs 79 ± 45 minutes, P <.0001). Conclusions Although both open and arthroscopic approaches to RCR had low morbidity, arthroscopy was associated with lower risks of any adverse event and return to the operating room during the initial 30-day postoperative period. Level of Evidence Level III, retrospective comparative study.