Background: Six transmembrane epithelial antigen 1 (STEAP1) is aberrantly expressed in cancers and could therefore be a potential biomarker. This study examined the connection between STEAP1 expression and clinical features/prognosis in cancer patients. Methods: Several databases were comprehensively searched for related published studies. The combination of hazard ratios (HRs), odd ratios (ORs), and 95% confidence intervals (95% CIs) was used to assess the role of STEAP1. The Cancer Genome Atlas (TCGA) dataset was used to estimate the prognostic value of STEAP1 in multiple cancer types, and several biological behaviors related to STEAP1 were evaluated by CancerSEA. Results: Searches of electronic databases revealed 7 relevant trials with 765 patients. A significant connection was found between high STEAP1 expression and worse overall survival amongst cancer patients (HR = 1.87, 95% CI: 1.49–2.34, p 0.001). In addition, a strong correlation was found between high STEAP1 expression and the occurrence of lymph node metastases (OR = 3.19, 95% CI: 1.26–8.09, p 0.001). Analysis of TCGA datasets verified that a higher level of STEAP1 expression is linked with reduced survival in many kinds of cancer. At the single cell level, STEAP1 expression was correlated with some tumor biological behaviors, such as angiogenesis, quiescence, and stemness. Conclusions: STEAP1 could regulate various biological functions in tumors and predict prognosis as a novel biomarker in a number of cancer types.