This study evaluates the performance of investment companies listed on the Tehran Stock Exchange (TSE) by employing systematic and nonsystematic risk measures, the Capital Asset Pricing Model (CAPM), and Arbitrage Pricing Theory (APT). The research aims to provide a comprehensive assessment of the risk-return tradeoff in the Iranian capital market, analyzing the extent to which these financial theories can explain stock price movements and investment company performance. Using historical stock price data, market indices, and macroeconomic factors, the study measures systematic risk (beta) and diversifiable risk across selected investment firms. CAPM is utilized to determine expected returns based on market risk premiums, while APT identifies multiple economic and financial variables influencing asset returns. The findings highlight the efficiency of these models in assessing investment performance, offering insights into portfolio diversification strategies and risk management practices within the Iranian financial market. The study contributes to the existing literature on asset pricing models in emerging markets, providing valuable implications for investors, financial analysts, and policymakers in Iran.