Although Frey syndrome is not life-threatening, it is identified as the most serious and widely recognized sequela of parotidectomy and has significant potential negative social and psychological implications. Several studies have investigated whether AlloDerm® implants prevent Frey syndrome effectively and safely, however, the conclusions are inconsistent. We aimed to evaluate the precise effectiveness of AlloDerm implants for preventing Frey syndrome after parotidectomy, using a systematic review and meta-analysis. We searched randomized and quis-randomized controlled trials in which AlloDerm implants were compared to blank controls for preventing Frey syndrome after parotidectomy, from the PubMed, Embase, the Cochrane Library and the ISI Web of Knowledge databases, without any language restriction. Two reviewers independently searched, identified, extracted data and assessed methodological quality. Relative risks with 95% confidence intervals were calculated and pooled. Five articles involving 409 patients met the inclusion criteria. Meta-analyses showed a significant 85% relative risk reduction in objective incidence (RR=0.15, 95% CI 0.08-0.30; P<0.00001) and 68% in subjective incidence (RR=0.32, 95% CI 0.19-0.57; P<0.00001) of Frey syndrome with AlloDerm implants; there was a significant 91% relative risk reduction in salivary fistula (RR=0.09, 95% CI 0.01-0.66; P=0.02); there was no statistical significance for the incidence of facial nerve paralysis (RR=0.96, 95% CI 0.84-1.09; P=0.51); there was no statistical significance for the incidence of seroma/sialocele (RR=1.36, 95% CI 0.66-2.80; P=0.40); there was a trend for a small effect in improving facial contour. Adverse events related to AlloDerm implants were not found. There is evidence that AlloDerm reduces the incidence of Frey syndrome effectively and safely, and also has the potential to improve facial contour and decrease salivary fistula. However, it is unclear whether AlloDerm implants improve facial contour and decrease other complications. Thus, further controlled evaluative studies incorporating more precise measures are required.