Malaria is a leading cause of mortality in children aged 5 years and below in Nigeria. Treatment guidelines stipulate among other recommendations, testing by microscopy or a rapid diagnostic test (RDT) before treatment. Non-adherence to these guidelines portends a challenge, especially among vulnerable under-five children. This study explored the factors influencing Nigerian public health workers' (HWs) adherence to these guidelines in under-five children. A review of literature published between 2011- 2023 was conducted on Web of Science, Ovid Embase, Medline, Global Health, CAB Abstracts, Scopus, and Global Index Medicus. Data was extracted and analyzed under 4 themes: diagnosis, compliance with test results, use of recommended treatment, post-treatment counselling and severe malaria management. Nineteen (19) studies were included for review. Training and supervision, RDT and antimalarial availability, good knowledge of, and positive perception of RDTs promoted adherence to mRDT use. A lack of confidence in RDTs and age (≥ 40 years) fuelled presumptive treatment, especially among clinicians. mRDT and artemisinin-based combination therapy (ACT) stockouts dissuaded HWs from adhering to case management guidelines. Caregiver pressure for treatment was identified as a barrier to compliance with test results. It is important to design context-specific strategies to improve adherence to guidelines for malaria case management, especially in under-five children. Training on the guidelines should be tailored, needs-based, and continuous, and HWs should be supportively supervised in implementing case management. Maintaining an adequate supply of quality-assured mRDTs and antimalarials can facilitate adherence to the guidelines.