This study aims to examine trends in outpatient psychotropic drug use among people with intellectual disabilities in Taiwan. The NHI outpatient medication records between January 1, 1997 and December 31, 2007 for people with intellectual disabilities were analyzed to observe the percent change, prevalence and prescription trends in psychotropic drugs. The overall prevalence of psychotropic medication increased from 17.82% to 23.22% during the study period. Results from stepwise logistic analysis demonstrated that females, the elderly, and individuals suffering from catastrophic disease were more prone to receive psychotropic drugs and that those with mild intellectual disability were less likely to receive psychotropic drugs. The percentage change in prescription rates of antipsychotics, hypnotics/sedatives, and antidepressants were 85.30%, 127.25%, and 167.50%, respectively, and the trends were statistically significant (p < 0.05). Taiwan's NHI program and off-label use of psychotropic drugs might have attributed to this trend.