Inappropriate antibiotic use in food-producing animals is associated with the emergence and spread of antibiotic resistance. In industrial broiler poultry farms in three districts of Kathmandu valley, Nepal, we assessed antibiotic use prevalence, and their classes, types, and quantities. A cross-sectional questionnaire study involving field visits to large poultry farms (flock size ≥ 3000) of the Kathmandu, Bhaktapur, and Lalitpur districts was conducted. Of 30 farms (total flock size 104,200; range 3000–6000), prevalence of antibiotic use was 90% (95% CI: 73–98%). Six (22%) farms used antibiotics as prophylaxis, while 21 (78%) used it for therapeutics. Seven antibiotics from six classes (including quinolones, macrolides, and polymyxins) were used. The most commonly used antibiotics were tylosin (47%), colistin (47%), and dual therapies with neomycin and doxycycline (33%). A total of 50,000 grams of antibiotics (total weight including active and inactive ingredients) were used (0.5 grams/chicken/45 days of flock life) with eight (26%) farms using more than two antibiotics. No farms had records on clinical indications for prophylaxis or treatment. No post-mortem records of sick birds were available. Prevalence of antibiotic use in broiler farms of Kathmandu valley is high and includes “highest priority critically important antibiotics” for human use, with direct implications on public health.