Background: Medication non-adherence is a public health problem at every level of the population, especially in older adults. Therefore, it is important to improve medication adherence in patients with chronic diseases to minimize early deaths, economic and social burden. The aim of this study was to evaluate the effect of cognitive behavioral intervention on medication adherence among elderly at Elibrahemya center, Sharkia governorate, Egypt. Design: A quasi-experimental study design was carried out. Setting: the study was conducted at Sharkiat Mobasher Village, Elibrahemya center, Sharkia Governorate, Egypt. Sample: A multistage cluster sampling technique of 60 elderly. Tools: Four tools were used to collect the study data: I) A structured interview questionnaire. II) Elderly knowledge regarding their chronic disease & medication structured interview questionnaire. III)Beliefs about Medicines Questionnaire (BMQ). IV) The General Medication Adherence Scale (GMAS). Results: The study results revealed statistically significant improvement in medication adherence score, knowledge regarding chronic disease and medication score & beliefs about medicine score among the studied elderly throughout the study phases pre, post and follow the intervention (P<0.001). Conclusion: The cognitive behavioral intervention is effective in improving the elderly's medication adherence practice. Recommendation: Patient- centered interventions to overcome adherence barriers. It is also recommended that future studies with more focus on modifiable risk factors of medication non adherence.