Failure to identify and treat depression and anxiety affecting 10% of patients with cancer, increases the disease burden. This study aimed to assess the psychological well-being of newly diagnosed patients in a tertiary healthcare centre in Lebanon. In this cross-sectional study, data were collected for 187 adult patients, from medical records and interviews using standardised questionnaires (Personal health questionnaire-9 (PHQ-9) and generalised anxiety disorder-7). Karnofsky performance status was also assessed, and incidence was calculated using descriptive statistics, chi-square, and T-tests. The rates of moderate or severe anxiety, minimal anxiety, mild depression, moderate or severe depression, and suicidality are 14.9%, 35.6%, 40.7% 22.7% and 6.2%, respectively. Participants with a past history of seeking help from mental health services (OR: 3.978, CI: (1.680–9.415), p = 0.002), those developing cancer-related complications (OR: 3.039, CI: (1.187–7.777), p = 0.020), and those who had an Eastern Cooperative Oncology Group of ≥2 (OR: 5.306, CI: (1.582–17.797), p = 0.007) were independently associated with depression (diagnosed with PHQ-9) in multivariate logistic regression analysis. Patients with cancer exhibit higher evidence of depression and anxiety and should have a thorough psychiatric history and additional psychiatric care.