Abstarct: Despite the importance of cost structure and investment in innovation, previous research on the impact of cost stickiness on financial performance and research and development (R&D) expenditures under conditions of economic uncertainty has been limited, and few studies have examined the simultaneous moderating effects of the economic environment. Most prior studies have addressed either financial performance or innovation separately, and the interaction between cost stickiness and uncertain economic conditions in Iranian companies, particularly listed firms, has largely been neglected. This research aims to fill this gap. Accordingly, the main objective of this study is to assess the impact of cost stickiness on financial performance and R&D expenditures in companies listed on the Tehran Stock Exchange under economic uncertainty, and to investigate the moderating role of inflation and economic fluctuations. The data were collected from 124 listed companies during the period 2014–2024 (1393–1403 Iranian calendar), and the analysis was conducted using panel least squares regression (PLS) with EViews 13 software. The findings revealed a significant relationship between cost stickiness and financial performance. Specifically, cost stickiness has a negative and significant effect on return on assets (ROA), indicating that higher cost stickiness reduces firm profitability. Moreover, a significant relationship was found between cost stickiness and R&D expenditures, with firms having higher fixed costs investing more in innovation. In addition, the results indicated that economic uncertainty moderates the relationship between cost stickiness and financial performance, such that under inflationary and uncertain economic conditions, the negative impact of cost stickiness on financial performance is partially mitigated. Similarly, economic uncertainty moderates the relationship between cost stickiness and R&D expenditures, reducing the positive effect of cost stickiness on R&D as firms adjust their innovative investments to manage economic risks. This study provides important practical and policy implications, including the need to optimize cost structures, ensure sustainable allocation of resources to R&D, and adopt flexible managerial policies to respond to economic uncertainty. The findings also offer a practical frxamework for strategic decision-making by managers and investors and pave the way for future research across different industries and markets.