Background: Although medicines have outstanding edges to the wellbeing of the general public, they still have the potential of actuating adverse drug reactions which are a significant reason for morbidity and mortality. The study aims to determine factors influencing adverse drug reaction reporting among patients. Method: This institutional based cross-sectional study was carried out within four selected health facilities in Kirinyaga County. Using a multistage sampling method, 360 patients were selected. A pretested interviewer-administered questionnaire was utilized for data collection. SPSS software was utilized to analyze data. Results: Two hundred and sixty-four (73.3%) patients were unaware of the patient alert card. Two hundred and sixty-eight (74.4%) participants concurred that it was their responsibility to report ADRs. One hundred and fourteen (31.7%) respondents opined that reporting should be done to serious and life threatening ADRs. One hundred and sixty-six (46.1%) patients experienced ADRs. Among them, 145 (87.3%) reported ADRs to health professionals. Seriousness of the ADRs and change of regimen encouraged reporting whereas fear due to unfriendly doctors discouraged reporting. Conclusion: The findings highlight gaps in knowledge and practice regarding ADR reporting. There is need for: regular sensitization, availing patient reporting tool in addition to implementing direct reporting by patients. Further investigations should be done at a national level to fully identify determinants of patient ADR reporting.