Among roadway users, bicyclists are considered vulnerable due to their high risk for injury when involved in a crash. Little is known about the circumstances leading to near crashes, crashes, and related injuries or how these vary by age and gender. The purpose of this study was to examine the rates and characteristics of safety-relevant events (crashes, near crashes, errors, and traffic violations) among adult and child bicyclists. Bicyclist trips were captured using Pedal Portal, a data acquisition and coding system which includes a GPS-enabled video camera and graphical user interface. A total of 179 safety-relevant events were manually coded from trip videos. Overall, child errors and traffic violations occurred at a rate of 1.9 per 100 min of riding, compared to 6.3 for adults. However, children rode on the sidewalk 56.4% of the time, compared with 12.7% for adults. For both adults and children, the highest safety-relevant event rates occurred on paved roadways with no bicycle facilities present (Adults = 8.6 and Children = 7.2, per 100 min of riding). Our study, the first naturalistic study to compare safety-relevant events among adults and children, indicates large variation in riding behavior and exposure between child and adult bicyclists. The majority of identified events were traffic violations and we were not able to code all risk-relevant data (e.g., subtle avoidance behaviors, failure to check for traffic, probability of collision). Future naturalistic cycling studies would benefit from enhanced instrumentation (e.g., additional camera views) and coding protocols able to fill these gaps.