Clinoptilolite is a natural zeolite which due to high surface area/volume ratio has found many applications in industries and medicine. Aspirin is a non-steroidal anti-inflammatory drug which is currently used as an anticoagulant, antinociceptive, antipyretic, and anti-inflammatory drug. It is an acidic drug which induces gastric irritation due to inhibition of cyclooxygenase I located in gastric mucosa. In the present work, adsorption and desorption of aspirin on Iranian clinoptilolite micronized particles were studied in acidic and relatively alkaline pHs. Effect of particle size of clinoptilolite was also investigated on adsorption and desorption of aspirin. Specific surfaces, particle sizes, and zeta potentials of clinoptilolite particles were also determined. Scanning electron micrograph was used to study the morphology and crystallinity of clinoptilolite particles. The results showed that adsorption and desorption of aspirin on clinoptilolite are particle size- and pH-dependent. The present work proposes clinoptilolite as an inexpensive, efficient, and non-toxic natural available microporous material for aspirin oral delivery.