The main objective of this book is to highlight the research work on the factors that influence investors'' investment decision making in Malaysia. The main issue is whether they are rational or irrational in their decision making behaviour. The findings from the current study however, found that Malaysian investors are rational investors. The researchers conclude that Malaysian investors are categorized as ‘savers'', ‘cautious and smart'' investors. This is due to the fact that they seek low-risk growth of investment such as mutual funds, property and money market. In the stock market investment, they make an effort to analyze share before decide to invest, use information from a variety of reliable sources and seek advice from knowledgeable people in their decision making process. For the success of their investment, it was found that they use technical analysis, company analysis and frame of reference as an evaluation tools for decision making. Herding was found to have negative impact to their investment success.