The relationship between firm size and profitability remains a contested issue within business economics, as prior research and theoretical perspectives provide inconclusive results. While economies of scale suggest that larger firms may achieve higher profitability through efficiency gains and specialization, the resource-based view emphasizes the importance of firm-specific resources and capabilities. This study examines the relationship between firm size and profitability among Swedish listed manufacturing firms, with particular focus on whether the relationship is linear or non-linear. The study applies a quantitative research design using panel data from 42 firms listed on Nasdaq Stockholm during 2018–2022, comprising 210 observations. Profitability is measured by Return on Assets (ROA), while firm size is operationalized as the natural logarithm of total assets. Multiple regression analysis is used to test both linear and quadratic relationships, including leverage, revenue growth, and year dummy variables as controls. The descriptive findings indicate a weak positive association between firm size and profitability. However, the regression results show no statistically significant relationship between firm size and ROA, neither in linear nor non-linear form. Overall, the findings suggest that firm size has limited explanatory power for profitability in the studied context, and that firm-specific resources and capabilities may be more important determinants of performance.