The research aims to analyze the translation of assertive speech acts in the Indonesian version of Agatha Christie's novel, Murder on the Orient Express. This research specifically aims to analyze: (i) the types of assertive speech acts found in the novel Murder on the Orient Express, (ii) the translation techniques used by the translator, (iii) the impact of these translation techniques on the illocutionary function of the translated speech acts, and (iv) translation quality, measured in terms of both accuracy and acceptability, addressing a gap in previous research that has not fully explored these aspects together.            The information was gathered from the original English novel and its Indonesian translation. Data was also collected from assessments by three expert raters. Data gathering was performed using a descriptive qualitative method, with analysis techniques based on Spradley's methods, and a Focus Group Discussion (FGD) was used to assess the quality of the translations.            A total of 156 assertive speech acts were identified and categorized as stating, reporting, asserting, claiming, and concluding. The most dominant translation technique employed was Established Equivalent, followed by Explicitation, Paraphrase, and Modulation. The study found that most translations were accurate and acceptable.            However, the analysis revealed that certain techniques like Reduction and Discursive Creation occasionally resulted in shifts in the illocutionary force or omissions, leading to a decrease in accuracy in 10 cases and acceptability in 8 cases. This highlights that while many translations effectively preserve the original meaning, the improper use of some techniques can compromise the quality of the translation.             The research concludes that the effectiveness of techniques such as Established Equivalent, Explicitation, and Paraphrase lies in their ability to balance semantic fidelity with cultural adaptation. The findings suggest that translators should prioritize these techniques while exercising caution with others that risk distorting the original meaning. The research also provides recommendations for future studies to expand on the analysis to further enhance the understanding of literary translation dynamics.