Caring for young people with first-episode psychosis (FEP) is challenging and can adversely affect carer well-being, with limited evidence-based support materials available. We aimed to examine whether completion of a self-directed problem-solving bibliotherapy among carers of young people with FEP led to a better experience of caring, less distress and expressed emotion, and better general health than carers who only received treatment as usual (TAU). A randomized controlled trial was conducted across two early-intervention psychosis services in Melbourne, Australia. A total of 124 carers were randomized to problem-solving bibliotherapy intervention (PSBI) or TAU and assessed at baseline, 6-week and 16-week follow-up. Intent-to-treat analyses were carried out and indicated that recipients of PSBI had a more favorable experience of caring than those receiving TAU, and these effects were sustained at both follow-up time points. Across the other measures, both groups demonstrated improvements by week 16, although the PBSI group tended to improve earlier. The PSBI group experienced a greater reduction in negative emotional evaluations of the need to provide additional support to young people with FEP than the TAU group by week 6, while the level of psychological distress decreased at a greater rate from baseline to 6 weeks in the PSBI compared with the TAU group. These findings support the use of problem-solving bibliotherapy for first-time carers, particularly as a cost-effective adjunct to TAU.