<p>Corner weld joints are widely used in structural, pressure-retaining, and fabricated components and are a frequent location for service-related failures due to their complex geometry and susceptibility to welding defects. Features such as variable penetration, sharp toe regions, root geometry, and limited probe access make reliable ultrasonic testing (UT) challenging and increase the risk of missed or inaccurately sized flaws. Phased array ultrasonic testing (PAUT) is increasingly applied to these joints because its electronic beam steering, focusing, and multi-angle capability allow improved inspection coverage. In practice, however, inspection reliability depends strongly on the selection and implementation of PAUT parameters. This review synthesizes published literature and field experience to examine how practical PAUT parameters—including probe frequency and bandwidth, wedge and probe selection, refracted and skew angles, focal depth, aperture size, scan strategies, and acquisition settings—affect signal quality, defect detectability, and sizing accuracy in corner weld inspections. Particular emphasis is placed on parameter-related limitations such as low signal-to-noise ratio, beam distortion, grating lobes, and imaging artifacts, which can lead to missed defects, false calls, and non-conservative integrity assessments. The review further clarifies how suboptimal inspection design constitutes a credible failure mechanism by propagating inspection uncertainty into fitness-for-service decisions. By consolidating parameter-sensitivity trends, reliability limitations, and reported mitigation strategies, this review identifies PAUT parameter combinations that consistently enhance the probability of detection while highlighting common inspection design practices that contribute to inspection unreliability. Overall, this paper provides actionable, reliability-focused guidance to support improved inspection design, safer integrity assessment, and failure prevention in corner weld joints.</p>