This study examines the validity of Greenblatt’s “Magic Formula,” a simple stock selection model, across Thailand and the US markets. The steps to screen out the stocks for the magic portfolio were adopted from Greenblatt’s “The Little Book That Still Beats the Market,” and the magic formula’s returns were compared to the market’s returns. SET index is chosen for the Thai stock market and S&P 500 is chosen for the US stock market. Sharpe ratio analysis is used to measure risk-adjusted return. Overall, this study suggests that the magic formula’s two factors, return on capital and earning yield, were able to produce a higher risk-adjusted return than the market index from 1993 to 2012 for 12 years in Thailand’s portfolio and 8 years in US portfolio. Thailand’s portfolio generates 24.3%, the annualized geometric return, comparing with 3%, that of the market during the tested period. In addition, US portfolio generates 12.7% comparing with 6.5% of the market.