Introduction There are concerns that the high incidence of medicine-related adverse events is compromising patient safety. System errors and human factors, particularly inadequate knowledge of pharmacotherapy, are significant causes of medication errors. Little has been published on the continuing professional education of radiographers. We report on a study undertaken in Finland between 2012 and 2014. Methods In this quasi-experimental study, we explored the relationship between radiographers' backgrounds (e.g., age, clinical experience, sex) and intravenous (IV) medication theoretical competence before (n = 77) continuing pharmacotherapy education delivered with two different learning methods, 1 to 2 weeks after (n = 56) and 6 months later (n = 37). Results After the education programs, younger age, less clinical experience, and education in higher education institute (University of Applied Sciences) were significantly associated with performing better than average (more than median score) in the IV pharmacotherapy knowledge test. Both immediately after education and 6 months later, more participants performed better than average and passed more than 80% of correct answers limit after simulation-based than web-based education, respectively. Discussion Continuing IV pharmacotherapy education improved theoretical medication competence, particularly for younger and less experienced radiographers. Evidence-based continuing education for radiographers is needed to assure patient safety.