It is common practice to augment efficacious treatment protocols for special populations (Durlak & DuPre, 2008), but this is often done before establishing that standard services are not appropriate. In this randomized controlled trial with families at risk or with a history of maltreatment (N = 151), we investigated the effectiveness of standard 12-session Parent-Child Interaction Therapy (PCIT). This is in contrast to other PCIT studies with similar parents, which have allowed for longer and sometimes variable treatment length and with modifications to PCIT protocol. After treatment and compared to Waitlist, mothers reported fewer child externalizing and internalizing behaviors, decreased stress, and were observed to have more positive verbalizations and maternal sensitivity. These outcomes were equivalent or better than outcomes of our previous PCIT trial with high-risk families (Thomas & Zimmer-Gembeck, 2011) when treatment length was variable and often longer. These findings support standard protocol PCIT as an efficacious intervention for families in the child welfare system.