Besides assessment of forensic patients’ risk of future violence and criminogenic needs, knowledge on their responsivity to treatment is equally important. However, instruments currently used for risk assessment are not sensitive enough for treatment evaluation. Therefore, the Instrument for Forensic Treatment Evaluation (IFTE) was developed. The IFTE is a treatment evaluation tool, which uses the dynamic risk items of the Dutch risk assessment tool, the HKT-R (Historical, Clinical, Future–Revised). The IFTE has an extended answering scale, which makes it more sensitive for measuring change and enables clinicians to monitor patients’ responsivity to treatment closely. This study examines the concurrent and predictive validity of the IFTE. We found moderate to strong correlations between IFTE items and HKT-30 items (the HKT-30 is the predecessor of the HKT-R), with work and therapy attendance, and positive drug tests. In addition, we found moderate to modest correlations between some IFTE items and work and therapy attendance in a 6-month follow-up period and modest to high discriminative power for some IFTE items for violence and drug use 6 months after the measurement. Given its good reliability and validity properties, and comprehensive but short-term nature, implementation of the IFTE in forensic practice likely improves individual treatment of forensic psychiatric patients and has high potential for risk management purposes.