This study aimed to investigate the efficacy of an online group counselling program based on Holland theory in improving career decision skills for a sample of grade 10th female students in Oman. Forty female students were involved in the study procedures based on their low scores on the career decision scale who were distributed randomly on two groups the experimental group (20 students) and the control group (20 students). The experimental group was attending 10 online group counselling sessions based on Holland theory in career counselling while the control group did not attend any treatment. The career decision-making scale was used that contained 27 items distributed on different dimensions: problem identification, seeking for alternatives, alternative balancing, and decision-making process. The results of Mann-Whitney revealed that there were statistical differences in the post-test scores for the experimental and control groups in career decision skills in favor of the experimental one. The Wilcoxson test results indicated that there were no statistical differences between the post-test scores and one-month follow-up scores of the experimental group which indicates the sustained effect of the counselling program. The study proposed some suggestions and recommendations for future studies.