ImportancePartners of colorectal cancer (CRC) survivors play a critical role in diagnosis, treatment, and survivorship. While financial toxicity (FT) is well documented among patients with CRC, little is known about long-term FT and its association with health-related quality of life (HRQoL) among their partners.ObjectiveTo understand long-term FT and its association with HRQoL among partners of CRC survivors.Design, Setting, and ParticipantsThis survey study incorporating a mixed-methods design consisted of a mailed dyadic survey with closed- and open-ended responses. In 2019 and 2020, we surveyed survivors who were 1 to 5 years from a stage III CRC diagnosis and included a separate survey for their partners. Patients were recruited from a rural community oncology practice in Montana, an academic cancer center in Michigan, and the Georgia Cancer Registry. Data analysis was performed from February 2022 to January 2023.ExposuresThree components of FT, including financial burden, debt, and financial worry.Main Outcomes and MeasuresFinancial burden was assessed with the Personal Financial Burden scale, whereas debt and financial worry were each assessed with a single survey item. We measured HRQoL using the PROMIS-29+2 Profile, version 2.1. We used multivariable regression analysis to assess associations of FT with individual domains of HRQoL. We used thematic analysis to explore partner perspectives on FT, and we merged quantitative and qualitative findings to explain the association between FT and HRQoL.ResultsOf the 986 patients eligible for this study, 501 (50.8%) returned surveys. A total of 428 patients (85.4%) reported having a partner, and 311 partners (72.6%) returned surveys. Four partner surveys were returned without a corresponding patient survey, resulting in a total of 307 patient-partner dyads for this analysis. Among the 307 partners, 166 (56.1%) were aged younger than 65 years (mean [SD] age, 63.7 [11.1] years), 189 (62.6%) were women, and 263 (85.7%) were White. Most partners (209 [68.1%]) reported adverse financial outcomes. High financial burden was associated with worse HRQoL in the pain interference domain (mean [SE] score, −0.08 [0.04]; P = .03). Debt was associated with worse HRQoL in the sleep disturbance domain (−0.32 [0.15]; P = .03). High financial worry was associated with worse HRQoL in the social functioning (mean [SE] score, −0.37 [0.13]; P = .005), fatigue (−0.33 [0.15]; P = .03), and pain interference (−0.33 [0.14]; P = .02) domains. Qualitative findings revealed that in addition to systems-level factors, individual-level behavioral factors were associated with partner financial outcomes and HRQoL.Conclusions and RelevanceThis survey study found that partners of CRC survivors experienced long-term FT that was associated with worse HRQoL. Multilevel interventions for both patients and partners are needed to address factors at individual and systemic levels and incorporate behavioral approaches.