Objective: Children are particularly vulnerable to experiencing medication incidents in hospitals. Making sound medication decisions is therefore of paramount importance. Prior research has principally described pharmacists' role in reducing medication errors. There is a dearth of information about pharmacists' interactions with pediatric hospital staff across disciplines in resolving medication issues. The aim of this study was to examine interdisciplinary medication decision making by pharmacists in pediatric hospital settings. Design: An ethnographic design was undertaken comprising observations, semi-structured interviews and focus groups. Audio-recorded data were analyzed thematically. Setting: The study was conducted in three wards of an Australian pediatric tertiary teaching hospital, comprising general surgical, gastroenterology, endocrinology, neurology, adolescent and rehabilitation settings. Participants: Pharmacists, registered nurses and doctors were recruited from diverse clinical wards following information sessions. Results: Pharmacists were central to complex pediatric medication decision making, intervening about dosage, administration, drug interactions and authorities. Pharmacists proactively contacted doctors and nurses about prescribing issues; conversely, staff routinely approached pharmacists for medication advice. Pharmacists were perceived as medication experts, their extensive knowledge valued in resolving complex issues: when off-label medications were prescribed, when protocols were absent or ambiguous, where tension existed between protocol adherence and patient safety, and where patients on multiple medications were at risk of medication error. Pharmacists had strong relationships with doctors and nurses, which had a bearing on pharmacists' input in interventions. Furthermore, pharmacists identified prescribing errors through strategies, such as case note review and medication reconciliation, although the lack of emergency department pharmacists and limited after-hours staffing posed challenges to both strategies. Conclusions: Pharmacists made a substantial and highly valued contribution to pediatric inter-professional medication decision making. These results provide new knowledge that informs theoretical developments of pharmacists' role in decision making.