A valid measure of oral malodor (halitosis) and associated quality of life is required for the complete assessment of treatment effectiveness. The purpose of this study was to analyze the psychometric and clinimetric validity of the Halitosis Associated Life-quality Test (HALT) questionnaire, a specific 20-item quality-of-life measure for halitosis. The HALT is a de novo designed tool based on patient interviews and literature review. The University Hospital was the setting for the prospective random non-controlled study design. The comparison between the evaluator’ scales on organoleptic testing and HALT scores was performed during the patient’s initial visit. HALT was completed by 33 and 16 patients at the initial visit and at 3 months after treatment commencement, respectively. Two treatment arms comprising an experimental arm including Caphosol rinse for xerostomia-associated halitosis, and an established treatment arm with laser cryptolysis were compared. Cronbach’s α was 0.93; coefficient alpha with deleted variables was between 0.92 and 0.94; equal length Spearman–Brown coefficient is 0.95. The Cronbach’s alphas of each split questionnaire were 0.85 and 0.88, respectively, and test–retest scores were highly correlated (r = 0.85). HALT scores were significantly associated with the scales of organoleptic test (F = 118, p < 0.001; r = 0.96, p < 0.001). HALT successfully measured each treatment arm and showed improvement (p < 0.002) in both arms. Although cryptolysis was more efficacious, the encouraging results of the Caphosol arm indicate that additional investigation is warranted. HALT proved a valid outcome measure for patients with halitosis, describes its burden and is sensitive to clinical change.