The paper presents a simplified method for calculation of resistance of a TCC slab in fire conditions. Within the method the tensile and the compressive failure criteria in the outermost fibres of the cross-section are checked. The influence of the fire is applied through one-dimensional charring of the timber part of the cross-section in accordance with current standards on reduction of properties of materials. The concrete-timber connection is assumed to be ideal during the determination of resistant moment of the TCC cross-section. On the other hand, the calculation of the deflection of the TCC slab is conducted with the reduction of the connection’s rigidity. The ineffective zone of the timber as well as the cracked tensile zone of concrete part do not contribute to the effective stiffness of the TCC slab. The method is validated against the results of full sized fire tests of one way spanning TCC slabs form literature. Calculated and experimentally determined midspan deflections and failure times of the TCC slabs are compared and their considerable agreement is observed. Due to its convenience and accuracy, the present simplified method represents a useful tool for designers of TCC structures in fire conditions.