Serum 1,3-β-d-glucan (BG) assay may be helpful as a marker for the diagnosis of Pneumocystis jiroveci pneumonia (PJP) and invasive fungal infection (IFI). We conducted a systematic review to assess the diagnostic accuracy of this assay. We searched MEDLINE, Web of Science, Cochrane Collaboration databases, Ichushi-Web, reference lists of retrieved studies, and review articles. Our search included studies of serum BG assay that used (i) positive cytological or direct microscopic examination of sputum or bronchoalveolar lavage fluid for PJP and (ii) European Organization for Research and Treatment of Cancer or similar criteria for IFI as a reference standard and provided data to calculate sensitivity and specificity. Only major fungal infections such as invasive candidiasis and invasive aspergillosis were included in the IFI group. Twelve studies for PJP and 31 studies for IFI were included from January 1966 to November 2010. The pooled sensitivity, specificity, diagnostic odds ratio (DOR), and area under the summary receiver operating characteristic curve (AUC-SROC) for PJP were 96% (95% confidence interval [95% CI], 92% to 98%), 84% (95% CI, 83% to 86%), 102.3 (95% CI, 59.2 to 176.6) and 0.96 (95% CI, 0.94 to 0.99), respectively. No heterogeneity was found. For IFI, the values were 80% (95% CI, 77% to 82%), 82% (95% CI, 81% to 83%), 25.7 (95% CI, 15.0 to 44.1), and 0.88 (95% CI, 0.82 to 0.93). Heterogeneity was significant. The diagnostic accuracy of the BG assay is high for PJP and moderate for IFI. Because the sensitivity for PJP is particularly high, the BG assay can be used as a screening tool for PJP.