Summary: This paper presents a low-complexity method for the direction-of-arrival (DOA) estimation of noncircular signals for coprime sensor arrays. The noncircular property is exploited to improve the performance of DOA estimation. To reduce the computational complexity, the rotational invariance propagator method (RIPM) is included in the algorithm. Firstly, the extended array output is reconstructed by combining the array output and its conjugated counterpart. Then, the RIPM is utilized to obtain two sets of DOA estimates for two subarrays. Finally, the true DOAs are estimated by combining the consistent results of the two subarrays. This illustrates the potential gain that both noncircularity and coprime arrays provide when considered together. The proposed algorithm has a lower computational complexity and a better DOA estimation performance than the standard estimation of signal parameters by the rotational invariance technique and Capon algorithm. Numerical simulation results illustrate the effectiveness and superiority of the proposed algorithm.