Abstract: Background: There is growing interest in the provision of parenting support to substance misusing parents.Methods: This pragmatic, multi-center randomized controlled trial compared an intensive one-to-one parenting program (Parents under Pressure, PuP) with Treatment as Usual (TAU) in the UK. Parents were engaged in community-based substance misuse services and were primary caregivers of children less than 2.5 years of age. The primary outcome was child abuse potential, and secondary outcomes included measures of parental emotional regulation assessed at baseline, 6 and 12-months. A prospective economic evaluation was also conducted. Results: Of 127 eligible parents, 115 met the inclusion criteria, and subsequently parents were randomly assigned to receive PuP (n = 48) or TAU (n = 52). Child abuse potential was significantly improved in those receiving the PuP program while those in TAU showed a deterioration across time in both intent-to-treat (p < 0.03) and per-protocol analyses (p < 0.01). There was also significant reliable change (recovery/improvement) in 30.6% of the PuP group compared with 10.3% of the TAU group (p < 0.02), and deterioration in 3% compared with 18% (p < 0.02). The probability that the program is cost-effective was approximately 51.8% if decision-makers are willing to pay £1000 for a unit improvement in the primary outcome, increasing to 98.0% at a £20,000 cost-effectiveness threshold for this measure. Conclusions: Up to one-third of substance dependent parents of children under 3-years of age can be supported to improve their parenting, using a modular, one-to-one parenting program. Further research is needed.