During the 2010-2011 US influenza season, 105 pediatric and 13 family practice offices participated in a prospective observational study of in-office influenza vaccination of children. Office characteristics, influenza vaccinations, and vaccination-related activities were reported. Among pediatric offices, first dose vaccination rates (2% to 60%), 2-dose compliance (11% to 100%), the duration of vaccine availability (60-302 days), and office visit type (well vs sick vs clinic) used for vaccinations varied greatly. Pediatric offices had higher vaccination coverage than family practice offices, offered vaccine longer, and administered more vaccinations during sick visits. Smaller offices and higher staff vaccination rates were associated with higher vaccination coverage. Smaller offices and video reminders in waiting rooms were associated with enhanced 2-dose compliance among children younger than 9 years. A greater understanding of interoffice variability in influenza vaccine delivery by US pediatric providers should allow for the creation of more effective strategies to improve pediatric influenza vaccination rates.