Objective To investigate the prevalence of psychotropic medication use and identify factors affecting the prescription of psychotropics among patients newly diagnosed with any of 8 common types of cancer. Methods This retrospective descriptive study examined data for patients newly diagnosed with breast, colorectal, liver, lung, ovarian, pancreatic, prostate, or stomach cancer between July 2009 and May 2014. The data were derived from a nationwide health claims database. The proportion of initial prescriptions for all oral psychotropics within 13 months of cancer diagnosis was analyzed by cancer type; the odds ratio (OR) for prescribing psychotropics was calculated using multivariable logistic regression models. Results A total of 14 661 patients were newly diagnosed with cancer. Psychotropics were prescribed for 6593 (45%) patients. The highest and lowest proportions of psychotropic prescriptions were recorded for patients with lung cancer (62.6%) and prostate cancer (35.1%), respectively. The strongest predictors for psychotropic prescriptions were chemotherapy (OR, 2.59; 95% confidence interval [CI], 2.31–2.91; P < .001), lung cancer (OR, 2.47; 95% CI, 2.16–2.83; P < .001), and surgery (OR, 2.12; 95% CI, 1.97–2.28; P < .001). Conclusions The prevalence of and predictors for an initial prescription of psychotropics identified a potential target population of cancer patients requiring psychiatric treatment, particularly soon after a diagnosis of cancer.