Background and Objective: Hospitalized patients in the Coronary Care Unit require the frequent blood sampling for diagnostic and treatment assessment. According to routine plan of unit, a new venipuncture was performed to obtain each blood sample. This causes damage and pain in patients. The current study was conducted to compare the effect of blood sampling by direct venipuncture with venous catheter on the blood biochemical results in patients hospitalized in CCU.Materials and Method: In this quasi- experimental study, 80 hospitalized patients were selected through purposive sampling in CCU in one of the teaching hospitals in Zahedan in 2015. At first in order to doing the biochemical tests, 5 cc blood sample was obtained from IV catheter and the same volume was obtained by direct venipuncture from another hand. Blood sample were assessed in terms of glucose, cholesterol, triglyceride, sodium, potassium, urea, creatinine and CRP. Data were analyzed using paired T- test and Pearson correlation coefficient test in SPSS 16.0.Results: The laboratory values of glucose, cholesterol, triglyceride, sodium, Potassium and CRP were not significant different between the two blood samples by venipuncture and venous catheter. But there was significant difference between the BUN level (p=0.004) and Creatinine in two methods (p = 0.015).Conclusion: According to the results, the venous catheter can be used for obtaining the blood sample and laboratory assessment. But, due to significant difference in level of BUN and creatinine test results, further studies are needed.