Background: The same conversion factors (k-factors) of Single CT (SECT) are applied to estimate the Effective Dose (ED) in Dual Energy Computed Tomography (DECT). However, k-factors for different organs need independently validating for DECT, due to the different conditions in DECT. Objective: This study aimed to calculate organ dose and k-factors in different imaging protocols (liver, chest, cardiac, and abdomen) for male and female phantoms. Material and Methods: This Monte Carlo Simulation study used Monte Carlo N-Particle (MCNP) code for modeling a Siemens Somatom Definition Flash dualsource CT scanner. The organ dose, dose length product, and k-factors were calculated for the Medical Internal Radiation Dose (MIRD) of male and female phantoms. Results: For the male phantom, the k-factors for the liver, chest, cardiac, and abdomen-pelvis imaging protocols are equal to 0. 020, 0. 012, 0. 016, and 0. 014 mSv. mGy−, 1cm−, 1, respectively. For the female phantom, the corresponding values are equal to 0. 026, 0. 023, 0. 036, and 0. 018, respectively. These values for DECT are different from those corresponding values for SECT, especially for the female phantom. Conclusion: The calculated k-factors for DECT can be used as reference values for the estimation of ED in DECT.