Background: Allergic rhinitis (AR) is a major non-communicable disease that affects the health-related quality of life (HRQoL) of patients. AR is significantly related to asthma also affecting HRQoL. However, data on HRQoL and symptom control in AR patients with comorbid asthma are lacking. Objective: To assess the differences of symptom control and HRQoL in AR patients with and without comorbid asthma. Methods: In this multicentre, cross-sectional study, patients with AR were screened and administered questionnaires of demographic characteristics and health conditions (symptoms/diagnosis of AR and asthma, disease severity level, and allergic conditions). HRQoL was assessed using a modified version of the RHINASTHMA questionnaire and symptom control was evaluated by a modified version of the Control of Allergic Rhinitis/Asthma Test (CARAT). Results: Out of 643 patients with AR, 500 (78%) had asthma as a comorbidity, and 54% had moderate-severe intermittent AR, followed by moderate-severe persistent AR (34%). Patients with both AR and asthma had significantly higher RHINASTHMA scores than the patients with AR alone (e.g., median RHINASTHMA-total score 84 vs. 48.5, respectively). Conversely, CARAT scores were significantly lower in AR with comorbid asthma than in the patients with AR alone (median CARAT-total score 16.5 vs. 23, respectively). Upon stratifying asthma based on severity, AR patients with severe persistent asthma had worse HRQoL and control than AR patients with mild persistent asthma. Conclusions: Our observation of poorer HRQoL and symptoms control in AR patients with comorbid asthma supports the importance of a comprehensive approach for the management of AR in case of a comorbid allergic condition.