When a report of child maltreatment is made, it is typical for both the police and CPS to investigate the allegations and in many States their co-involvement in the investigation is required by law. Despite their required working relationship, the two disciplines have at times expressed apprehension at working together. The current article reviews the practice and empirical literature regarding the investigative coupling of law enforcement and CPS and presents a secondary analysis of CPS outcome data to analyze the implications of police and CPS co-involvement in child maltreatment investigations. The literature is contradictory regarding the implications of police and CPS investigative coupling; some sources report that the combined power of the two agencies benefits both the investigations and the outcomes for children and their families. On the other hand, critics maintain that a certain amount of friction between the two agencies can hamper investigations and produce heavy-handed outcomes. Secondary data analysis was conducted on data derived from the National Survey of Child and Adolescent Well-Being, a survey of over 5,500 cases investigated between 1999 and 2000 by CPS in 36 different States. The findings indicated that police involvement in CPS investigations resulted in the allegations being judged more credible and in the family receiving more support services. Overall, the results indicate that the police do not hamper CPS investigations and in fact may improve the effectiveness of child maltreatment investigations. The authors call for coordinated child maltreatment investigations in every community. Future research should focus on the quality and appropriateness of interventions resulting from police co-involvement in child maltreatment investigations. Tables, notes, references