This study aimed to establish whether the modified Schirmer test could serve as a diagnostic tool for dry mouth, that is, whether it could reliably measure salivary film at selected locations within the oral cavity, and to identify levels of sensitivity/specificity and determine reference values. Therefore, a cross-sectional study (N = 120, mean age 63.5 [SD 13.9] years) was performed. The test was used at five locations (hard palate; buccal mucosa in molar region at 4 mm above occlusal plane; anterior tongue; lower lip; mouth floor), and results were recorded after 1, 2 and 3 min. A statistically significant discriminatory ability of the Schirmer test for the unstimulated salivary flow rates could be shown for the palate (at 3 min), buccal mucosa (at 1 min), mouth floor (at 1 min), and tongue (at 2 and 3 min) (areas under the curve 0.64-0.68), with individual sensitivity/specificity values depending on test location/time points. Thus, the modified Schirmer test has potential to become a simple and reproducible instrument for the detection of dry mouth based on low unstimulated salivary flow rates in dentistry and especially outreach care. Care must be taken concerning intraoral test location and measurement time.