Background: Toxic oil syndrome (TOS) is a multisystemic disease due to a massive intoxication. To evaluate physical and mental health of TOS patients, we used the Health Assessment Questionnaire (HAQ) and the Patient Health Questionnaire–9 (PHQ-9). Additionally, we correlated both questionnaires with the results of the Short Form-36v2 (SF-36v2) Health Survey obtained in the same patients’ sample. Methods: 895 TOS patients who participated in the prior SF-36v2 study were invited to participate. We described patients’ demographic and clinical characteristics, HAQ and PHQ-9 results. HAQ and PHQ-9 scores were correlated to the standardised SF-36v2 results obtained in our previous study. Results: In total, 828 (92.5%) TOS annual follow-up and HAQ and 810 (90.5%) PHQ-9 valid questionnaires were analysed. Participants’ average age was 65.4 (Standard Deviation (SD): 13.4), 521 (62.9%) were women, 725 (87.6%) reported having at least other chronic disease and 789 (95.3%) an additional TOS-related health problem. Average scores were 0.91 (SD: 0.83) for HAQ, 35.8 (SD: 10.1) for PCS and 37.8 (SD: 11.6) for MCS. Overall, 467 (57.7%) participants had moderate/severe depression (PHQ-9 ≥ 10), but only 229 (49.6%) of them reported having a depression diagnosis. Correlation between questionnaires was very strong for HAQ and physical function SF-36v2 dimension and moderate/fair for the rest of combinations. Conclusions: TOS cohort presented low/very low health status measured with SF-36v2, moderate difficulties in performing daily activities according to HAQ, and a high prevalence of major depression measured with PHQ-9. High proportion of undiagnosed depression was detected, proving PHQ-9 useful in terms of detecting and promoting depression diagnosis in the cohort.