Misfit layered Ca3Co4O9 samples have been fabricated by solid-state reaction method. X-ray diffraction analysis showed that the samples have the c-axis oriented monoclinic structure. The temperature dependence of the DC magnetization of the sample fabricated was investigated in an applied field of 2000 Oe. Magnetization of the sample increased smoothly down to 20 K, then increased rapidly with decreasing temperature, suggesting a transition to the ferrimagnetic phase. M-H analysis indicated a paramagnetic behavior between 20 and 300 K and hysteretic effect below 20 K which corresponds to paramagnetic-ferrimagnetic phase transition. The ferrimagnetisms are most likely caused by interlayer coupling between the Ca2CoO3 and CoO2 subsystems in unit cell.