This study examines the role of internal auditing and auditor training in mitigating financial statement manipulation at companies listed on the Hanoi Stock Exchange (HNX). The focus of the study is the impact of internal auditor training and the level of internal audit implementation on earnings management through discretionary accruals. Financial statement data from 69 companies during the period 2022–2025 were used to measure earnings management according to the Kothari et al. (2005) model, where the level of earnings manipulation (represented by discretionary accruals) is the dependent variable. The independent variables include (i) internal auditor training and (ii) characteristics/effectiveness of internal auditing, collected from internal datasets at selected companies. The analysis results show that the majority of listed companies have established internal audit departments, but the level of investment in professional training is limited and uneven among companies. Quantitatively, companies with more effective internal audit activities and a focus on auditor training tend to record lower discretionary provisioning levels, implying reduced earnings management behavior. Therefore, the study recommends strengthening internal control mechanisms before publishing financial statements, establishing close operational links between the internal audit department and the audit committee, and standardizing and expanding training programs for auditors to improve their ability to detect and prevent financial statement manipulation