DESIGN:Prospective cohort. OBJECTIVE:To explore the association between preseason assessments of (1) isometric hip adductor and abductor strength using a novel field test and (2) the Copenhagen Hip and Groin Outcome Score (HAGOS) and subsequent hip/groin injury in male professional soccer players. METHODS:In total, 204 male elite soccer players from 10 professional A-League and English Football League Championship clubs underwent assessments of hip adductor and abductor strength and completed the HAGOS in the 2017-2018 preseason. All subsequent hip/groin injuries were reported by team medical staff. Data reduction was conducted using principal-component analysis. The principal component for the HAGOS and 3 principal components for strength and imbalance measures were entered, with age and prior hip/groin injury, into a multivariable logistic regression model to determine their association with prospectively occurring hip/groin injury. RESULTS:Twenty-four players suffered at least 1 hip/groin injury throughout the 2017-2018 season. The principal component for between-limb abduction imbalance (peak strength in the preferred kicking limb - nonpreferred limb) (odds ratio [OR] = 0.58; 95% confidence interval [CI]: 0.38, 0.90; P = .011), the principal component for peak adduction and abduction strength (OR = 0.71; 95% CI: 0.51, 1.00; P = .045), and the principal component for the HAGOS (OR = 0.77; 95% CI: 0.62, 0.96; P = .022) were independently associated with a reduced risk of future hip/groin injury. Receiver operating characteristic curve analysis of the whole model revealed an area under the curve of 0.76, which indicates a fair combined sensitivity and specificity of the included variables but an inability to correctly identify all subsequently injured players. CONCLUSION:Hip abduction imbalance favoring the preferred kicking limb, higher levels of hip adductor and abductor strength, and superior HAGOS values were associated with a reduced likelihood of future hip/groin injury in male professional soccer players. J Orthop Sports Phys Ther 2020;50(5):234-242. Epub 17 Sep 2019. doi:10.2519/jospt.2020.9022.