Background: Primary ciliary dyskinesia (PCD) is a rare genetic disorder caused by the malfunction of motile cilia and a specific etiology of adult bronchiectasis of unknown prevalence. A better understanding of the clinical phenotype of adults with PCD is needed to identify individuals for referral to diagnostic testing. Research Question: What is the frequency of PCD among adults with bronchiectasis; how do people with PCD differ from those with other etiologies; and which clinical characteristics are independently associated with PCD? Study Design and Methods: We investigated the proportion of PCD among the participants of the Prospective German Non-CF-Bronchiectasis Registry (PROGNOSIS) study; applied multiple imputation to account for missing data in 64 (FEV₁), 58 (breathlessness), 26 (pulmonary exacerbations), and two patients (BMI), respectively; and identified predictive variables from baseline data using multivariate logistic regression analysis. Results: We consecutively recruited 1,000 patients from 38 centers across all levels of the German health care system. Overall, PCD was the fifth most common etiology of bronchiectasis in 87 patients (9%) after idiopathic, postinfective, COPD, and asthma. People with PCD showed a distinct clinical phenotype. In multivariate regression analysis, the chance of PCD being the etiology of bronchiectasis increased with the presence of upper airway disease (chronic rhinosinusitis and/or nasal polyps; adjusted OR [aOR], 6.3; 95% CI, 3.3-11.9; P <.001), age < 53 years (aOR, 5.3; 95% CI, 2.7-10.4; P <.001), radiologic involvement of any middle and lower lobe (aOR, 3.7; 95% CI, 1.3-10.8; P =.016), duration of bronchiectasis > 15 years (aOR, 3.6; 95% CI, 1.9-6.9; P <.001), and a history of Pseudomonas aeruginosa isolation from respiratory specimen (aOR, 2.4; 95% CI, 1.3-4.5; P =.007). Interpretation: Within our nationally representative cohort, PCD was a common etiology of bronchiectasis. We identified few easy-to-assess phenotypic features, which may promote awareness for PCD among adults with bronchiectasis. Clinical Trial Registration: ClinicalTrials.gov; No.: NCT02574143; URL: www.clinicaltrials.gov