Penelitian ini bertujuan menguji pengaruh ukuran perusahaan dan struktur modal terhadap kinerja keuangan. Ukuran perusahaan diukur melalui total asset dan total revenue, sedangkan struktur modal diwakili oleh debt to asset ratio (DAR) dan debt to equity ratio (DER). Kinerja keuangan diukur melalui return on asset (ROA) dan Tobin’s Q. Data penelitian berasal dari 767 perusahaan manufaktur di Indonesia, Singapura, Malaysia, Thailand, dan Filipina selama 2014–2023, yang diambil dari S&P Capital IQ menggunakan purposive sampling. Analisis dilakukan dengan metode data panel menggunakan model estimasi fixed effect. Hasil penelitian menunjukkan bahwa total asset memiliki pengaruh positif signifikan terhadap ROA tetapi negatif signifikan terhadap Tobin’s Q. Total revenue memiliki pengaruh positif signifikan terhadap ROA dan Tobin’s Q. DAR memiliki pengaruh negatif signifikan terhadap ROA tetapi positif tidak signifikan terhadap Tobin’s Q. DER menunjukkan pengaruh positif tidak signifikan terhadap ROA tetapi negatif signifikan terhadap Tobin’s Q. / This study aims to examine the effect of firm size and capital structure on financial performance. Firm size is measured through total assets and total revenue, while capital structure is represented by the debt to asset ratio (DAR) and debt to equity ratio (DER). Financial performance is assessed using return on assets (ROA) and Tobin’s Q. The study uses secondary data from 767 manufacturing companies operating in Indonesia, Singapore, Malaysia, Thailand, and the Philippines during the 2014–2023 period, sourced from S&P Capital IQ through a purposive sampling method. The analysis was conducted using panel data methodology with a fixed effect estimation model. The results show that total assets have a significant positive effect on ROA but a significant negative effect on Tobin’s Q. Total revenue has a significant positive effect on both ROA and Tobin’s Q. DAR has a significant negative effect on ROA but an insignificant positive effect on Tobin’s Q. DER demonstrates an insignificant positive effect on ROA but a significant negative effect on Tobin’s Q.