Purpose: Taste alterations (TA) and oral discomfort in cancer patients are neglected side effects of the disease and treatments. They contribute to poor appetite, decrease food intake and affect quality of life, leading to adverse outcomes such as malnutrition and depression. The study aimed to explore TAs in relation to other oral conditions causing discomfort in cancer patients. Additionally, the correlation between patients’ acidity of saliva and experienced TAs and oral discomfort was evaluated. Methods: A case study including 100 patients diagnosed with cancer receiving chemotherapy or immunotherapy. Data were collected using two questionnaire forms: the Chemotherapy-induced Taste Alteration Scale (CiTAS) and an additional information questionnaire. Saliva samples were collected for each patient and measured with a pocket pH meter. Data were analysed using descriptive statistics, and comparisons were performed using the Kruskal–Wallis H test, Mann–Whitney U test and Fisher’s exact test. Results: The prevalence of reported TAs was 93%. Patient age, oral discomfort and swallowing difficulty were found to be significant factors for experienced TAs (p < 0.05). No correlation between patients’ acidity of saliva and reported TAs and oral discomfort was found. Conclusion: CiTAS proved to be a convenient tool to collect information about TAs in cancer patients. Using the CiTAS tool, a high prevalence (93%) of reported TAs in cancer patients receiving chemo- or immunotherapy was found. CiTAS provides a fast and cheap recognition of symptoms and causes of TAs that can be addressed.