Background: Allergen immunotherapy (AIT) may have a long-term disease modifying effect. The aim of this study is to demonstrate the long-term benefit of MCT®-associated allergoid pollen SCIT (MCT®-associated -AIT) on allergic rhinitis (AR) and asthma in clinical practice. Methods: In this retrospective Real-World-Evidence (RWE) study the impact of AIT on the progression of AR and onset of need for asthma medication was analyzed using a German longitudinal database. Anonymized prescription data of AR patients and exactly matched control patients aged from 5-65 years were analyzed. Results: Significantly less patients treated with MCT®-associated-AIT did receive prescriptions for symptomatic AR medication in the follow up period vs. control group (OR: 0.27; p < 0.001). Further, significantly less asthmatic patients under MCT®-associated-AIT did receive prescriptions for asthma medications (OR: 0.48; p = 0.004). In addition, the prescriptions of AR and asthma medication for MCT®-associated-AIT patients were significantly reduced in the follow-up vs. baseline and control group (24.2% and 35.6%, respectively, p < 0.001).The probability of asthma medication onset in non-asthmatic patients during follow-up was significantly reduced for AIT patients compared to controls (OR: 0.77, p = 0.001). All endpoints were significant for children/adolescents and adults in the individual analyses. Conclusions: This study gives evidence for long-term benefits up to 9.5 years of MCT®-associated-AIT on the need for AR and new-onset asthma medication in AR patients and asthma medication in asthmatics in an RWE setting.