Background: Oral mucositis (OM) and infectious complications frequently interrupt cancer therapy. Interprofessional oral-care bundles, delivered by nurses with dental professionals (dentists, dental hygienists, dental assistants), may mitigate these harms. We aimed to synthesize evidence on the effects of nursing–dental oral-care bundles on (1) OM incidence/severity, (2) infection and febrile neutropenia (FN), and (3) treatment tolerance (dose reductions/interruptions). Methods: We conducted a systematic review (PRISMA-aligned) of randomized and non-randomized studies in patients receiving chemotherapy, radiotherapy or hematopoietic stem-cell transplantation (HSCT). Eligible interventions were multicomponent oral-care programs delivered by nursing and/or dental teams; outcomes were OM, infection/FN, and treatment tolerance. Results: Twelve original studies (five randomized trials and seven observational/quasi-experimental studies) met inclusion. Across chemotherapy and HSCT, professional oral health care and nurse-implemented hygiene protocols consistently reduced OM severity; several studies also reported lower FN or infection signals. In head-and-neck radiotherapy, comprehensive oral management protocols and nurse-led mucositis programs reduced severe OM and supported completion of planned radiotherapy. Evidence for direct effects on dose reductions was most explicit in a phase III trial in breast cancer receiving targeted therapy, which showed clinically meaningful stomatitis prevention and improved manageability. Conclusions: Interprofessional oral-care bundles improve clinically important toxicity outcomes and likely support treatment continuity. Implementation in oncology services, especially those with established nursing workforces and dental assistants, appears feasible and valuable. Standardization of bundle components and reporting (including infection endpoints and treatment tolerance) is the next step.