Background and Objectives: Aerosol drug administration is the primary treatment modality of otitis media with effusion (OME). An automatic manosonic aerosol generator (AMSA) delivers, with an acoustic overpressure, a therapeutic dosage of a drug by inhalation of the aerosol. However, available studies confirming their efficacy, especially in adults, are limited. Therefore, this pilot single-arm trial aimed to analyze changes in adults with OME following AMSA treatment. Materials and Methods: A group of 36 patients (mean age 51.4 years) with OME underwent a three-day treatment with inhaled mucolytic and steroids administered by AMSA. Tympanometry (tympanogram type, volume, compliance, pressure, and gradient) was performed to measure middle ear effusion before and after the intervention. Results: Following the intervention, partial and complete OME remission was observed in, respectively, 29 (81%) and 14 (39%) patients. The tympanogram type of the affected ears differed between baseline and after intervention measurements (p < 0.001). Tympanometry-based normalization, improvement deterioration and no change were observed in, respectively, 34 (68%), 1 (2%) 2 (4%), and 13 (26%) affected ears. Following the intervention, we observed an increase in continuously assessed middle ear volume (∆median 0.19 mL, p = 0.002) and pressure (∆median 142 daPa, p < 0.001), as well as a higher proportion of patients achieving categorical normalization of compliance (16% vs. 54%, p < 0.001) and pressure (28 vs. 64%, p < 0.001). Conclusions: Treatment efficacy was not affected by age, sex, or season of recruitment (all p > 0.05). The results of this pilot study are encouraging, however, the use of AMSA management of OME in adults needs to be verified in future studies.