Background The reasoning bias of jumping to conclusions (JTC) consists of a tendency to make assumptions having little information. Objective The aim of this study was to estimate the differences in neuropsychological functioning between recent onset psychotic patients who jump to conclusions and those who do not jump to conclusions. Materials and methods One hundred and twenty-two patients with a recent onset of a psychotic disorder were assessed with three JTC tasks and a neuropsychological battery exploring verbal learning, memory, attention, psychomotor speed, visuoperceptual abilities, working memory, problem solving, executive functioning. Results A total of 29.7% (n=36) of the individuals jumped to conclusions in Task 1, 14.0% (n=17) in Task 2, and 15.7% (n=19) in Task 3. People who jump to conclusions in three tasks scored significantly worse in many neuropsychological domain deficits, including attention (p<0.001–0.020), psychomotor speed (p<0.001), working memory (p<0.001–0.040), and executive functioning (p<0.001–0.042). Discussion The present study demonstrates that JTC is present even in early stages of the illness, and that there is a relationship between JTC and neuropsychological functioning.