Steganographic techniques can be utilized to conceal data within digital images with small or invisible changes in the perceived appearance of the image. Generally, five main objectives are used to assess the performance of steganographic algorithms which include embedding capacity, imperceptibility, security, robustness and complexity. However, steganographic algorithms hardly take all of these factors into account. In this paper, a novel steganographic algorithm for digital images is proposed based on the pixel-value differencing (PVD) and modified least-significant bit (LSB) substitution (MDPVD-MLSB) techniques to address most of aforementioned objectives. Although there are many techniques for concealing data within pixels, the restricting factor is always the amount of bits adjusted in every pixel. Therefore, the main contributions of this paper aim to achieve a balance between the amount of embedded data, the level of acceptable distortion, as well as providing high level of security. The performance of this algorithm has been extensively evaluated in terms of embedding capacity, peak signal-to-noise ratio (PSNR) and structural similarity index measure (SSIM). Simulation results and comparisons with six relevant algorithms are presented to demonstrate the effectiveness of this proposed algorithm.