This study examines the impact of passengers on driver’s crash risk on freeways using the records of the crashes that occurred on a 36.3-mile stretch of Interstate-4 freeway (I-4) in Orlando, Florida over 3 years (2002-2004). Bivariate probit models were developed to identify the correlation between potentially inter-related responses of various passenger and crash characteristic variables. The results of the models showed that there exists strong impact of passengers on crash risk. It was observed that drivers tend to display safer driving behavior when they are accompanied by passengers, and higher number of passengers reduces driver’s crash risk. It was also found that not only driver’s and passenger’s age affects crash risk, but also does their gender - young male drivers’ crash risk increases when they are accompanied by young male passengers compared to young female passengers. The findings in this study provide insights into how passengers have an impact on driver behavior and traffic safety in various conditions.