The aim of this study was to determine the most important risk factors in the development of otitis media with effusion (OME) in children with adenoid hypertrophy. A total of 539 patients undergoing surgery for adenoid hypertrophy (AH Group) (n = 429) or adenoid hypertrophy and otitis media with effusion (AH + OME Group) (n = 110) between February 2012 and February 2018 constituted the study group. Data were obtained on neonatal history (breastfeeding, bottle feeding), past health and medical history (presence of atopy or allergic rhinitis, snoring at night, cough, tonsillitis in the past 12 months), environmental factors (presence of pets, attending to daycare centers, district of school), family history (passive smoking at home, number of siblings, family size, parental education), and family income. The groups did not differ from each other for age (p = 0.684) and gender (p = 0.728). Our data support the presence of atopy or allergic rhinitis (p < 0.001), frequent (> 5) tonsillitis (p < 0.001), attending to daycare centers (p < 0.001), exposure to smoke (p < 0.001), having 3 or more siblings (p < 0.001), and 4 or more people in the household (p < 0.001) as the main risk factors for OME. Comprehensive knowledge of modifiable risk factors found in this study could help to minimise the complications of OME in children.