Bedside functional hemodynamic assessment has gained in popularity in the last years to overcome the limitations of static or dynamic indexes in predicting fluid responsiveness. The aim of this systematic review and metanalysis of studies is to investigate the reliability of the functional hemodynamic tests (FHTs) used to assess fluid responsiveness in adult patients in the intensive care unit (ICU) and operating room (OR). MEDLINE, EMBASE, and Cochrane databases were screened for relevant articles using a FHT, with the exception of the passive leg raising. The QUADAS-2 scale was used to assess the risk of bias of the included studies. In-between study heterogeneity was assessed through the I indicator. Bias assessment graphs were plotted, and Egger's regression analysis was used to evaluate the publication bias. The metanalysis determined the pooled area under the receiving operating characteristic (ROC) curve, sensitivity, specificity, and threshold for two FHTs: the end-expiratory occlusion test (EEOT) and the mini-fluid challenge (FC). After text selection, 21 studies met the inclusion criteria, 7 performed in the OR, and 14 in the ICU between 2005 and 2018. The search included 805 patients and 870 FCs with a median (IQR) of 39 (25-50) patients and 41 (30-52) FCs per study. The median fluid responsiveness was 54% (45-59). Ten studies (47.6%) adopted a gray zone analysis of the ROC curve, and a median (IQR) of 20% (15-51) of the enrolled patients was included in the gray zone. The pooled area under the ROC curve for the end-expiratory occlusion test (EEOT) was 0.96 (95%CI 0.92-1.00). The pooled sensitivity and specificity were 0.86 (95%CI 0.74-0.94) and 0.91 (95%CI 0.85-0.95), respectively, with a best threshold of 5% (4.0-8.0%). The pooled area under the ROC curve for the mini-FC was 0.91 (95%CI 0.85-0.97). The pooled sensitivity and specificity were 0.82 (95%CI 0.76-0.88) and 0.83 (95%CI 0.77-0.89), respectively, with a best threshold of 5% (3.0-7.0%). The EEOT and the mini-FC reliably predict fluid responsiveness in the ICU and OR. Other FHTs have been tested insofar in heterogeneous clinical settings and, despite promising results, warrant further investigations.