Low alloy steels (LAS), frequently used for pressure-containing equipment in subsea applications, are susceptible to hydrogen embrittlement when exposed to seawater environments under cathodic protection (CP), which can result in a reduction of toughness and ductility. Fracture toughness, which is an indication of a material’s resistance to crack propagation and unstable crack growth, is often determined from laboratory tests for design verification analysis or fitness-for-service applications. In hydrogen charging environments such as deaerated saltwater under CP, the fracture toughness is typically measured using either an unloading compliance (UC) or a rising displacement DCPD test method, both of which are described for air testing in the current ASTM E1820 standard. In this study, slow load rate fracture toughness tests on compact tension C(T) specimens using both test methods on the same heat of material are performed and compared. The tests are performed in a deaerated saltwater under CP environment using the same targeted K-rate of 0.005N/mm3/2/s. The UC test method is performed with a clip gauge for load-line displacement (LLD) and in-situ crack depth measurement, and the rising displacement DCPD test method infers LLD indirectly and uses DCPD for crack depth prediction. A comparison of the test results indicated a 35-65% increase in the calculated ???????? fracture toughness of the material when using the rising displacement DCPD test method.