This study aimed to investigate whether Internet-based cognitive behavioural therapy intervention (ICBT) for individuals with tinnitus had an indirect effect on the third-party disability noticed by significant others (SOs). Significant Others Questionnaire (CTSOQ). Individuals with tinnitus completed standardized self-reported outcome measures for tinnitus severity, anxiety, depression, insomnia, hearing-related quality of life, tinnitus cognitions, hearing disability, and hyperacusis. In total, 194 pairs of individuals with tinnitus and their SOs participated. The impact of third-party disability experienced by SOs was significantly reduced after individuals with tinnitus undertook the ICBT intervention (d = 0.41). This reduced SOs with severe difficulties from 52% to 35%. The remaining impact was mild for 30% and moderate for 35%. SOs with higher baseline difficulties and SOs who were partners (e.g., spouses) were less likely to notice indirect benefits from intervention undertaken by their family members. There was a moderate positive correlation between the post-intervention CTSOQs and the clinical variables of tinnitus severity and depression. Third-party disability may be reduced as an indirect effect of individuals with tinnitus undertaking ICBT. Including SOs of individuals with tinnitus within the rehabilitation process may add additional benefits, and such involvement should be encouraged.