In the present world Investment decision is most important phenomena. Investment is current sacrifice for future benefits, So while making investment decisions we have to keep different things in mind. Investment decisions are influenced not only by their fundamentals but also depend on different factors. One factor is the biasness of any investor to their investment, biasness depends on the cognition and emotions, because some investors use them as heuristic for the investment decision instead of fundamentals. Keeping this in view, this paper shows how cognitive biasness (i.e. Representativeness, Adjustment and Anchoring, Leniency) effects the investment decisions over the fundamentals. This study also show different types of investors which depicts significant relation of Representativeness, Adjustment and Anchoring, Leniency with investment decisions over fundamentals, and explain under which biasness an investor become more optimistic and moderate for investment decisions. While considering Representativeness biasness over fundamentals investor become more optimistic, In Adjustment and Anchoring biasness investor show moderate behavior about investment decision, and In Leniency biasness investor also take investment decision over optimistically.