This study examined the effects of cognitive restructuring intervention program of rational-emotive behavior therapy on irrational thoughts/behaviors arising from adverse childhood stress in Nigeria. The participants (n = 26) are the identified victims of adverse childhood stress who met the criteria for inclusion through self-report questionnaire. The treatment process is guided by the adverse childhood stress management manual. It consists of 12 weeks of full intervention and 2 weeks of follow-up meetings. The study used repeated measures ANOVA in order to see the improvement of each participant and across control and treatment groups' thoughts/behaviors after the intervention program. The results show that sex differences do not determine experience of adverse childhood stress. Through cognitive restructuring intervention program of rational-emotive behavior therapy, irrational thoughts/behaviors arising from adverse childhood stress experience were significantly reduced in the treatment group when compared to the control group. Significant improvement was also observed at the end of the intervention of the treatment group. The implication for research and practice were discussed in line with these outcomes. Finally, the study stressed the importance of a follow-up study in Nigeria that would assess irrational beliefs and one or more measures of PTSD symptoms or emotional disturbance.