Increased water content in rocks can result in a decline in their strength and an increase in deformation, which can lead to geological disasters such as landslides and tunnel collapses. Hence, rock characteristics with respect to water content need to be investigated for the purposes of conducting risk assessments and implementing preventive measures. In this study, the influence of the water content on rock failure patterns and acoustic emission (AE) characteristics was investigated. Uniaxial compression tests and numerical simulations with the PFC2D software were used to study the evolution process of microcracks and failure patterns in red sandstones with different water contents. The increases in the water content reduced the rock strength, Young's modulus, ratio of strain to peak strain in the elastic deformation stage, maximum energy of a single AE event, and average AE energy. The red sandstone specimens in the saturated state formed a shear macroscopic fracture surface, whereas those in the natural state formed a failure pattern in which shear failures and splitting failures coexisted. The red sandstone failure pattern in the dry state remained between these two conditions. The average frequency centroid of AEs revealed the precursory characteristics for critical failures of red sandstone with different water contents. The findings of this study are useful for future risk assessment and disaster prevention studies.