PurposeAmyotrophic lateral sclerosis (ALS) is a progressive motor impairment leading to early death. Religiousness is one of the factors potentially alleviating the psychological burden of patients. However, its role might vary according to cultural context. Our study aimed to analyze religiosity, and its clinical, psychological and socio-demographic correlates in ALS patients and controls, comparing two European countries with different cultural backgrounds.Methods268 Polish and German ALS patients, including 18 with locked-in syndrome (LIS) and 198 healthy controls (HC) were interviewed about religiousness, quality of life (Qol), depression, functional status and pain. A follow-up was conducted on 71 patients.ResultsPolish subjects had a significantly higher level of public, private and general religiosity than the German sample. Importantly, we found no difference in total and public religiousness between ALS patients and HC within either population. Only the private religiousness was significantly higher in German patients compared to controls. In the same sample, private religiousness correlated with functional impairment due to disease progression. In ALS groups and LIS patients, religiousness did not correlate with any disease-associated factors: disease duration, pain, Qol or depression. Follow-up comparisons in the ALS group revealed worsening functional status, increased depression and no significant change in religiosity.ConclusionsReligiosity was linked to the cultural background rather than ALS. Generally, it did not correlate with clinical, psychological and socio-demographic parameters and was stable throughout disease progression. The only exception was the relationship between the functional decline and private religiosity among German patients.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11136-023-03383-4.