The tensile, fatigue and creep properties of carbon fiber filled poly(ether-ether-ketone) or PEEK were compared by employing injection and compression molding processes. The specimens with different initial fiber lengths were fabricated using compression and injection molding methods. The effects of fiber length on mechanical properties are evident in cases of specimens made by compression molding. But, the injection molded samples show no differences in tensile and fatigue strengths contingent on the initial fiber length. Similarly, the effects of fiber volume fraction on tensile and fatigue strengths are more evident for the compression molded specimens than the injection molded specimen. For the creep properties, even the injection molded specimens show some improvement for long reinforcing fibers especially as temperature is increased. When the influence of time and temperature is considered, the effects of fiber length on mechanical properties are very significant. Also, these results represent the significant fiber damage during injection molding.