Emergency department (ED) admissions have been rising over the last decades, especially in countries without any effective gate-keeping functions. Integration of walk-in clinics into the hospital might reduce ED-visits. Over a longer period, however, the additional service of a walk-in clinic might attract even more patients, nullifying an initial decrease in patients for the ED. This study aimed to determine short- and intermediate-term changes after the implementation of a hospital-integrated walk-in clinic. This is an observational study using routinely-collected health data. Study setting was the ED of a large tertiary care hospital in Austria, a country with universal health care and no regulations regarding level of care. ED-visits were compared between before (2015) and after (2017 and 2018) establishment of a hospital-integrated walk-in clinic. Total ED-visits decreased from 87,624 in 2015 to 67,479 in 2017, and 67,871 in 2018 (p < 0.001), mainly due to a decrease in non-urgent (ESI 4 & 5) cases (45,715 (54.1%) in 2015; 33,142 (51.3%) in 2017; 30,846 (47.5%) in 2018; short term OR non-urgent vs. urgent: 0.89 (95% CI 0.88–0.91); intermediate term OR urgent vs. non-urgent: 0.76 (95% CI 0.78–0.75)). A total of 2611 (13%) (2017) and 1714 (8.5%) (2018) patients were referred back to the ED. After the introduction of the walk-in clinic, ED-visits declined significantly. This remained stable over a two-year period. Reduction in ED-visits was mainly due to low-acuity patients not requiring admission to the hospital. •After the introduction of a walk-in clinic, ED-visits declined significantly.•The absolute number of patients admitted to the hospital did not change.•The reduction in ED-visits was due to low-acuity patients not requiring admission to the hospital.•Relevant difference in decline of visits between different sub-specialities.•This effect remained stable over a two-year period.