Objectives: About 5–10% of asthmatics do not respond well to standard treatment plan. Occupational exposure may be one of the factors that can be linked with treatment failure. The aim of the study was to assess the prevalence of work-related asthma (WRA) among adult asthmatics under follow up in an outpatient allergy clinic and to create a useful tool for detecting individuals with possible WRA. Material and Methods: Preliminary 5-question questionnaire designed to recognize WRA was presented to 300 asthmatics. All patients with positive preliminary verification along with 50 subjects from control group were asked to fill up a detailed questionnaire. The WRA was diagnosed by positive match for asthma symptoms in combination with workplace exposure indicated in the detailed WRA questionnaire followed by confirmation of each WRA case by detailed exposure analysis. Results: Work-related asthma was recognized in 63 subjects (21% of study group). The preliminary questionnaire has 76.9% sensitivity and 94% specificity in recognition of WRA. Occupational exposure to irritants is a risk factor of WRA recognition (relative risk (RR) = 2.09 (1.44:3.03)). Working in exposure-free environment is a factor against WRA recognition (RR = 0.38 (0.24:0.61)). Among subjects with work-related asthma, the uncontrolled course of the disease is significantly more frequent (p = 0.012). Subjects with WRA more often report sickness absenteeism due to asthma than those without WRA (9.6% vs. 3.2%, respectively), but the observed differences did not reach the statistical significance. Conclusions: Short 5-question questionnaire seems to be a promising tool to detect individuals with possible work-related asthma in the outpatient setting for further evaluation and additional attention.