Patients with head and neck cancer have complex needs that affect many basic functions of life and contribute to substantial psychosocial problems. The aim of this study was to evaluate the effectiveness of a problem-focused intervention for patients with psychosocial dysfunction who had completed treatment for head and neck cancer. Using a quasi-experimental design, 54 participants who were above pre-determined cutoff points for psychosocial dysfunction (hospital and depression scale, work and social adjustment scale) were given the opportunity to self-select into either the experimental group for the psychosocial intervention programme which was delivered in an individualised format, with bibliotherapy as an adjunct, or the control group for usual care. Analysis of covariance results demonstrated a reduction in psychological distress (anxiety, p = 0.001; depression, p = 0.005), improving social functioning (p = 0.048) and quality of life scores (p = < 0.05) for the experimental group, all of which were sustained into the 3-month follow-up period. No such improvements were evident for the control group. This study suggests that head and neck cancer patients with post-treatment psychosocial dysfunction can benefit from a problem-focused psychosocial intervention. Such evidence can inform practice, policy and future research, aimed at improving post-treatment quality of life for patients with head and neck cancer.