Harmful pediatric medication errors are common in hospitals and health systems. Understanding what products are involved in these errors is important in the prevention of future errors. We used data from a voluntary medication error reporting system (MEDMARX) and identified 816 harmful outcomes involving 242 medications during a 5-year period. Eleven medications accounted for more than one third of reported errors (n = 261 or 34.5%). Wrong dosing and omission errors were common and were associated with therapeutic classes such as opioid analgesics (e.g., morphine and fentanyl), antimicrobial agents (e.g., vancomycin and gentamicin), and antidiabetic agents (e.g., insulin). Older commonly used agents still resulted in a substantial number of harmful pediatric medication errors and should be included in the focus of patient safety activities.