A recently published article harshly criticized forensic practitioners operating in Slovenia for not including in their assessments any tests specifically designed to assess negative distortion (Areh, 2020). To promote better forensic assessment practice and stimulate future research on symptom and performance validity assessment in Slovenia, the current study translated the Inventory of Problems-29 (IOP-29; Viglione & Giromini, 2020) and its recently developed memory module (IOP-M; Giromini et al., 2020) into Slovene language and tested their validity and effectiveness by conducting a simulation/analogue study. Among 150 volunteers, 50 completed the IOP-29 and IOP-M under standard instructions; 50 were asked to respond as if they suffered from depression; and 50 were asked to respond pretending to suffer from schizophrenia. Statistical analyses showed that (1) the IOP-29 discriminated well between simulators and honest test-takers (d ≥ 3.56), demonstrating the same effectiveness when inspecting feigned depression (sensitivity = 88%) and feigned schizophrenia (sensitivity = 88%) at an almost perfect specificity (98%); (2) the IOP-M identified 50% of simulators of depression and 80% of simulators of schizophrenia at perfect specificity (100%); and (3) combining the results of the IOP-29 with those of the IOP-M notably improved classification accuracy so as to demonstrate incremental validity. Taken together, these findings provide initial support for using the IOP-29 and IOP-M in applied settings in Slovenia. Limitations related to the design of the study and recommendations for further research are provided.