Mass gatherings pose a risk for tuberculosis (TB) transmission and reactivation of latent TB infection. The annual Hajj pilgrimage attracts 2 million pilgrims many from high TB-endemic countries. We evaluated the burden of undiagnosed active pulmonary TB in pilgrims attending the 2015 Hajj mass gathering. We conducted a prospective cross-sectional study in Mecca, Kingdom of Saudi Arabia, for nonhospitalized adult pilgrims from five high TB-endemic countries. Enrollment criteria were the presence of a cough and the ability to produce a sputum sample. Sputum samples were processed using the Xpert MTB-RIF assay. Data were analyzed for drug-resistant TB, risk factors, and comorbidities by the country of origin. Of 1,164 consenting pilgrims enrolled from five countries: Afghanistan (316), Bangladesh (222), Nigeria (176), Pakistan (302), and South Africa (148), laboratory results were available for 1,063 (91.3%). The mean age of pilgrims was 54.5 (range = 18-94 years) with a male to female ratio of 2.6:1; 27.7% had an underlying comorbidity, with hypertension and diabetes being the most common, 20% were smokers, and 2.8% gave a history of previous TB treatment. Fifteen pilgrims (1.4%) had active previously undiagnosed drug-sensitive pulmonary TB (Afghanistan [12; 80%], Pakistan [2; 13.3%], and Nigeria [1; 6.7%]). No multidrug-resistant TB cases were detected. Pilgrims from high TB-endemic Asian and African countries with undiagnosed active pulmonary TB pose a risk to other pilgrims from over 180 countries. Further studies are required to define the scale of the TB problem during the Hajj mass gathering and the development of proactive screening, treatment and prevention guidelines.