The work introduces a novel image watermarking technique that undergoes optimization through the application of the swarm intelligence algorithm known as the firefly algorithm. This algorithm is utilized to determine the optimal value for the embedding factor, responsible for striking a balance between robustness and imperceptibility. As a security measure, the proposed approach involves scrambling the watermark image using the Arnold transform before directly embedding it into the cover image. Robust image watermarking is achieved through a combination of DCT and DWT transforms applied to various grayscale images. Two distinct logo images are employed as watermarks in this study. To assess robustness, the proposed method is subjected to various image processing attacks, and the normalized correlation value between the original and the extracted watermark is calculated. Experimental results are presented, showcasing the method’s ability to withstand a range of image-processing attacks. The findings highlight the excellent performance of the proposed technique in terms of both robustness and imperceptibility.