Introduction: Hearing loss adversely impacts communication, cognitive function, and quality of life, yet early detection among adults remains inadequate. Despite the availability of portable, cost effective tablet-based audiometric screening tools, national-level prevalence data on adult hearing loss in Mongolia are scarce, and no large-scale screening studies in primary health care settings have been conducted to date. Goal: This study aimed to determine the prevalence of screen-detected hearing loss among adults in Ulaanbaatar, evaluate its association with age and test frequency, and identify associated factors. Material and Methods: A cross-sectional study was conducted at primary health care clinics across nine districts of Ulaanbaatar (2024–2025), enrolling 2,335 adults (≥18 years). Hearing screening was performed using the MAICO easyTone device with DD65 v2A headphones at 500–6000 Hz (30 dB HL at 500 Hz; 20 dB HL at remaining frequencies), with ambient noise monitored per ANSI S3.1-2008. Each ear was classified as Pass or Refer at each frequency. Outcomes included screen-detected hearing loss (SD-HL), speech-frequency hearing loss (SD SFHL, 500–2000 Hz), and high-frequency hearing loss (SD-HFHL, 4000–6000 Hz), each categorized as bilateral or unilateral. Associated factors were assessed by univariable and multivariable logistic regression. Results: SD-HL was identified in 37.2% of participants (bilateral: 31.5%; unilateral: 5.7%), SD-SFHL in 30.6%, and SD-HFHL in 36.3%. Prevalence increased markedly with age, from 29.9% (40–49 years) to 96.6% (≥70 years) (p<0.001). On multivariable logistic regression, male sex was inversely associated with a positive screening result (OR=0.65, 95% CI: 0.42–0.99, p=0.049). Conclusion The findings of this study confirm that the MAICO easyTone tablet-based hearing screening device is a feasible and appropriate tool for the early detection of hearing loss among adults in routine primary health care settings in Ulaanbaatar. The high prevalence of screening-detected hearing loss underscores the urgent need to establish adult hearing screening programs in Mongolia. Future studies should include standard audiometric confirmation in participants with positive screening results to determine the diagnostic validity of this hearing screening approach.