To systematically review the available evidence for arthroscopic repair of chronic massive rotator cuff tears and identify patient demographics, pre- and post-operative functional limitations, reparability and repair techniques, and retear rates. Medline, Embase, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched to identify all clinical papers describing arthroscopic repair of chronic massive rotator cuff tears. Papers were excluded if a definition of "massive" was not provided, if the definition of "massive" was considered inappropriate by agreement between the 2 reviewers, or if patients with smaller tears were also included in the study population. Study quality and clinical outcome data were pooled and summarized. There were 18 papers that met the eligibility criteria; they involved 954 patients with a mean age of 63 (range, 37 to 87), 48% of whom were female. There were 5 prospective and 13 retrospective study designs. The overall study quality was poor according to the Modified Coleman Methodology Score. Of the 954 repairs, 81% were complete repairs and 19% were partial repairs. The follow-up range was between 33 and 52 months, and the mean duration between symptom onset and surgery was 24 months. Single-row repairs were performed in 56% or patients, and double-row repairs were performed in 44%. A pooled analysis demonstrated an improvement in visual analog scale from 5.9 to 1.7, active range of motion from 125° to 169°, and the Constant-Murley score from 49 to 74. The pooled retear rate was 79%. Arthroscopic repair of chronic massive rotator cuff tears is associated with complete repair in the majority of cases and consistently improves pain, range of motion, and functional outcome scores; however, the retear rate is high. Existing research on massive rotator cuff repair is limited to poor- to fair-quality studies. Level IV, systematic review including Level IV studies.