Patient education materials (PEMs) are commonly used for patient education. This study assessed readability, format quality, accuracy, understandability and actionability of printed asthma PEMs available in primary care in Singapore. Primary care in Singapore is provided by island-wide polyclinics and private general practices. We invited the three polyclinic healthcare groups and private general practices the Primary Care Research Network to submit asthma-related PEMs. Readability was assessed using Simple Measure of Gobbledegook (SMOG) and Flesch-Kincaid (FK) score. Format quality was assessed using "Clear-print and large-print golden rules" from UK Association for Accessible Formats (UKAAF). Understandability and actionability were evaluated using Patient Education Materials Assessment Tool - Printed. Three pulmonologists assessed content accuracy. Thirty leaflets were assessed. SMOG and FK estimated 93% (mean 9.3, range 5-14, SD 1.8) and 47% (mean 6.8, range 2.4-9.9, SD 2.0) exceeded the recommended sixth-grade reading level, respectively. About a third (37%) were fully concordant with UKAAF guidelines, with poor format quality contributed by small font size, poor text emphasis methods, and not using left-aligned text. Leaflets generally scored well in both understandability (mean 84%) and actionability (mean 72%). Thirteen leaflets were inaccurate, 92% of which contained at least one inaccuracy judged to have potentially harmful consequences to patients, including wrong emergency advice. While understandability and actionability are adequate, current asthma PEMs are limited by inappropriately high reading levels, poor format quality and inaccuracies. Healthcare professionals need to assess patients' reading abilities and ensure PEMs are accurate and suitable for their patients.