This paper presents a new concept of frequency modulated chaos shift keying system (FM-CSK) based on a modified Chua’s circuit and chaotic synchronization. The proposed solution can be potentially used for communication systems in wireless sensor networks (WSN), where the physical security of data transmission, efficient modulation and demodulation, analog-digital and digital-analog conversion is of high importance. The mathematical model of the drive-response system based on a modified Chua’s circuit, described by a system of four differential equations and nonlinear function, is a core of the offered communication system. The FM-CSK system concept is validated by MATLAB/Simulink simulation with a baseband additive white Gaussian noise (AWGN) channel. Approaches for the performance enhancement of the communication system are discussed and validated.