This paper aims to uncover the ideological differences between China and the United States (U.S.) regarding the East Sea (also known as the South China Sea) (hereafter ES) dispute by analyzing online news discourse. Specifically, by adopting van Dijk’s socio-cognitive approach to critical discourse analysis, the study analyzes English news reports from top media outlets in China (Global Times, China Daily) and the U.S. (The New York Times, The Washington Post) between 1 to 31 August 2023. Through qualitative analysis, the study interprets linguistic features that reflect each country’s media outlets’ underlying ideologies and then uncovers the differences between their ideologies. In addition, quantitative analysis identifies frequent discursive features that represent ideologies. Theoretically, the article contributes to the application of van Dijk’s Ideological Square theory in exposing ideologies in online media discourse. Practically, it helps construct a critical perspective on how Chinese and American online media report on the ES dispute and the involved nations based on their contrasting ideologies. Overall, by linking ideologies and discourse, the research elucidates how language conveys and shapes ideologies to promote national interests.This paper aims to uncover the ideological differences between China and the United States (U.S.) regarding the East Sea (also known as the South China Sea) (hereafter ES) dispute by analyzing online news discourse. Specifically, by adopting van Dijk’s socio-cognitive approach to critical discourse analysis, the study analyzes English news reports from top media outlets in China (Global Times, China Daily) and the U.S. (The New York Times, The Washington Post) between 1 to 31 August 2023. Through qualitative analysis, the study interprets linguistic features that reflect each country’s media outlets’ underlying ideologies and then uncovers the differences between their ideologies. In addition, quantitative analysis identifies frequent discursive features that represent ideologies. Theoretically, the article contributes to the application of van Dijk’s Ideological Square theory in exposing ideologies in online media discourse. Practically, it helps construct a critical perspective on how Chinese and American online media report on the ES dispute and the involved nations based on their contrasting ideologies. Overall, by linking ideologies and discourse, the research elucidates how language conveys and shapes ideologies to promote national interests.