Background: The aim of this study was to analyze the relationship between breastfeeding duration and adenoid size, snoring and acute otitis media (AOM). Methods: We analyzed the medical history of children admitted to the ENT outpatient clinic in 2022 and 2023, reported symptoms, ear, nose and throat (ENT) examination, and flexible nasopharyngoscopy examination of 145 children aged 3–5 years. Results: Breastfeeding duration of 3 and 6 months or more had a significant effect on the reduction of snoring (p = 0.021; p = 0.039). However, it had no effect on the adenoid size, mucus coverage and sleeping with an open mouth. Snoring was correlated with open mouth sleeping (p < 0.001), adenoid size with a 75% A/C ratio or more (p < 0.001), and adenoid mucus coverage in the Mucus of Adenoid Scale by Nasopharyngoscopy Assessment—MASNA scale (p = 0.009). Children who were breastfed for less than 3 months had more than a four-fold greater risk of snoring. There was a statistically significant correlation between AOM and gender (p = 0.033), breastfeeding duration in groups fed 1, 3 or 6 months or more (p = 0.018; p = 0.004; p = 0.004) and those fed with mother’s breast milk 3 or 6 months or more (p = 0.009; p = 0.010). Moreover, a correlation was found between adenoid size and mucus coverage, tympanogram, and open-mouth sleeping (p < 0.001). Independent factors of snoring in 3- to 5-year-old children were breastfeeding duration of less than 3 months (p = 0.032), adenoid size with an A/C ratio of 75% or more (p = 0.023) and open mouth sleeping (p = 0.001). Conclusions: Children breastfed for 3 and 6 months or more exhibited reduced rates of snoring. There was no effect of breastfeeding duration on adenoid size in children aged 3 to 5 years, suggesting that the link between breastfeeding duration and snoring is primarily associated with craniofacial development and muscle tone stimulation. A breastfeeding duration of 1 month or more plays a key role in reducing the rate of AOM. The mother’s milk plays a protective role against AOM. The presence of mucus might be responsible for snoring in preschool children. A medical history of breastfeeding should be taken into consideration when snoring children are suspected of adenoid hypertrophy.