Background and purposeExposure to intimate partner violence (IPV) is the most investigated form of maltreatment in Ontario, Canada. Given the potential for negative outcomes for children exposed to IPV, a better understanding of these cases is needed to provide the most optimal service response. The purpose of this paper is to examine the the increase in exposure investigations between 2008 and 2013. Three forms of exposure to IPV are considered in this study: (1) direct witness to physical violence, (2) indirect exposure to physical violence, and (3) exposure to emotional violence. Methods: The study used the Ontario Incidence Study of Reported Child Abuse and Neglect (OIS) data from 2008 and 2013. The OIS is a cyclical, cross sectional provincial child welfare study conducted every five years. Changes in the characteristics of IPV were examined by exploring key variables including the incidence of the specific form of IPV, referral source, and decisions made by child protection workers. Results: There were an estimated 22,347 investigations for exposure to IPV in 2008 and an estimated 31,300 investigations 2013. The overall substantiation rate for this type of investigation also increased with some important variations between subtypes. The number of substantiated investigations for exposure to emotional violence increased significantly between 2008 and 2013, from a rate of 4.21 investigations per 1000 children to 7.16 investigations per 1000 children. There was also a slight increase in the rate of investigations for direct witness to physical violence, but this increase was not statistically significant. In 2013, cases for exposure to emotional violence were 1.6 times more likely to be opened for ongoing child protection services than in 2008, while the rate of transfer to ongoing child welfare services for other exposure subtypes remained unchanged. The main sources of referral for IPV exposure investigations were police (59%), custodial parents (12%), and schools (9%). The proportion of police referrals has remained relatively stable between 2008 and 2013, but referrals by schools and custodial parents have changed within subtypes. Referrals by custodial parents for exposure to emotional violence investigations have doubled. Referrals by schools for direct witness to physical violence investigations have grown by a factor of 2.2. Conclusions and Implications: The continued increase in investigations referred for children’s exposure to IPV is concerning given that the service response remains unchanged. Custodial parents appear to be one of the primary sources of this increase. These results have important policy and practice implications and suggest that a true differential service response is needed for child protection cases referred for exposure to IPV, particularly exposure to emotional violence. These cases would benefit from a more comprehensive response by professionals, including police, shelter and support services, child protection, and schools. Better service coordination and inter-agency collaboration may also prevent families from being re-referred to child protection services.