Purpose: The aim of this study was to update the clinical practice guidelines for the use of basic oral care (BOC) interventions for the prevention and/or treatment of oral mucositis (OM). Methods: A systematic review was conducted by the Mucositis Study Group of the Multinational Association of Supportive Care in Cancer/International Society for Oral Oncology (MASCC/ISOO). The body of evidence for each intervention in each cancer treatment setting was assigned an evidence level. The findings were added to the database used to develop the 2013 MASCC/ISOO clinical practice guidelines. Based on the evidence level, one of the following three guideline determinations was possible: Recommendation, Suggestion, No guideline possible. Results: A total of 17 new papers across six interventions were examined and merged with a previous database. Based on the literature, the following guidelines were possible. The panel suggests that the implementation of multi-agent combination oral care protocols is beneficial for the prevention of OM during chemotherapy, head and neck (H&N) radiation therapy (RT), and hematopoietic stem cell transplantation (Level of Evidence III). The panel suggests that chlorhexidine not be used to prevent OM in patients undergoing H&N RT (Level of Evidence III). No guideline was possible for professional oral care, patient education, saline, and sodium bicarbonate, and expert opinion complemented these guidelines. Conclusions: The evidence supports the use of multi-agent combination oral care protocols in the specific populations listed above. Additional well-designed research is needed on the other BOC interventions prior to guideline formulation.