The performance of the accounting and auditing professions in an integrated manner contributes to the support of the economic decisions to invest, especially in the stock market through building a homogeneous system of information that can enable the decision maker to rationalize his decisions, so the aim of the research is to find out the role of the efforts of auditor to rationalize the investment decisions through a field study in which (98) lists of survey were distributed for (63) authorized

auditors and (35) employees of the financial brokerage companies. (96) of them were recollected. Two research hypotheses were put. The research found a strong relationship between efforts of auditors and rationalizing investment decisions, and also a lack of differences between the averages of the respondents attributed to general statements in the presence of such a relationship. The research recommended to increase the efficiency of efforts of auditors as well as the efficiency of investment decisions by providing factors affecting both of them.