Multilevel converters are mostly applied for medium-voltage high-power applications. Flying-capacitor-based multilevel converters such as flying capacitor multicell (FCM) and modified FCM (MFCM) are promising breeds of multilevel converters. Considering the advantages of MFCM converter over conventional FCM converter, and noting that conduction power loss investigation can be very advantageous in the design phase of multilevel converters, this paper presents an analytical approach to calculate and analyze conduction power losses in MFCM converters. First, the rms and average currents of the insulated-gate bipolar transistors (IGBTs) and anti-parallel diodes are analytically calculated by considering the associated duty cycle of each IGBT/diode in terms of the converter modulation index, load current, and load power factor. Numerical results of the derived closed-form equations to calculate the rms and average currents of IGBTs/diodes are compared with simulation results. All the simulation and analytic results agree well with each other which validate the derived closed-form equations. Afterwards, the obtained equations for rms and average current computations are utilized to calculate the conduction power losses in a 12.4MVA 3.3kV 9-level (line-to-line) MFCM converter. A 2.5kV 1.5kA IGBT module from ABB is considered as the power switch in the performed study for MFCM converter.