This paper explores the joint optimization of transmit beamforming and movable antenna (MA) positions in a cognitive radio (CR) system to maximize received signal power at a secondary receiver (SR) while mitigating co-channel interference to multiple primary receivers (PRs). The authors leverage the capabilities of fluid antennas (FAs) and MAs to create favorable channel conditions within a confined region. They propose an alternating optimization (AO) algorithm that combines successive convex approximation (SCA) and discrete sampling to solve the complex optimization problem. Theoretical analyses demonstrate that MAs can achieve maximum-ratio transmission (MRT) and effective interference mitigation under certain conditions. Numerical results show that the proposed AO algorithm outperforms conventional fixed-position antennas (FPAs) and other baseline schemes, particularly in terms of received signal power and interference mitigation. The study highlights the potential of MAs in enhancing the performance of CR systems.This paper explores the joint optimization of transmit beamforming and movable antenna (MA) positions in a cognitive radio (CR) system to maximize received signal power at a secondary receiver (SR) while mitigating co-channel interference to multiple primary receivers (PRs). The authors leverage the capabilities of fluid antennas (FAs) and MAs to create favorable channel conditions within a confined region. They propose an alternating optimization (AO) algorithm that combines successive convex approximation (SCA) and discrete sampling to solve the complex optimization problem. Theoretical analyses demonstrate that MAs can achieve maximum-ratio transmission (MRT) and effective interference mitigation under certain conditions. Numerical results show that the proposed AO algorithm outperforms conventional fixed-position antennas (FPAs) and other baseline schemes, particularly in terms of received signal power and interference mitigation. The study highlights the potential of MAs in enhancing the performance of CR systems.