This study aimed at evaluating the efficacy of an online CBT intervention with limited therapist contact targeting a range of posttraumatic symptoms among evacuees from the 2016 Fort McMurray wildfires. One hundred and thirty-six residents of Fort McMurray who reported either moderate PTSD symptoms (PCL-5 > 23) or mild PTSD symptoms (PCL-5 > 10) with mod-erate depression (PHQ-9 > 10) or subthreshold insomnia symptoms (ISI > 8) were randomized either to a treatment (n = 69) or a waitlist condition (n = 67). Participants were on average 45 years old, and mostly identified as White (82%) and as women (76%). Primary outcomes were PTSD, depression, and insomnia symptoms. Secondary outcomes were anxiety symptoms and disability. Signifi-cant Assessment Time x Treatment Condition interactions were observed on all outcomes, indicating that access to the treatment led to a decrease in posttraumatic stress (F[1,117.04] =12.128, p = .001; d = .519, 95% CI = .142- .895),depression (F[1,118.29] = 9.978, p = .002; d = .519, 95% CI = .141-.898) insomnia (F[1,117.60] = 4.574, p = .035; d = .512, 95% CI = .132-.892), and anxiety (F[1,119.64] = 5.465, p = .021; d = .421, 95% CI = .044- .797) symptom severity and disability (F[1,111.55] = 7.015, p = .009; d = .582, 95% CI = .200-.963). Larger effect sizes (d = 0.823-1.075) were observed in participants who completed at least half of the treatment. The RESILI-ENT online treatment platform was successful to provide access to specialized evidence-based mental health care after a disaster.