<p>Rare earth cobalt-based magnetic materials, renowned for their exceptional magnetic properties, are widely utilized in commercial and scientific applications. The effects of Tb content on the structure and magnetic properties of Pr_1−xTb_xCo₃ (<i>x</i> = 0.0–1.0) compounds have been systematically investigated in this work. It is found that, the Pr_1−xTb_xCo₃ compounds mixed with light and heavy rare earths retain a rhombohedral structure of the PuNi₃-type. Due to the lanthanide contraction effect, lattice constants and unit cell volume decrease with increasing Tb content. And, the coercivity (<i>H</i>_c) shows a trend of first increasing and then decreasing, while the saturation magnetization (<i>M</i>_s) is opposite. At 300 K, the optimized value <i>H</i>_c = 7.53 kOe occurs when the Tb content was 0.6 and is dominated by the nucleation field; but at 10 K the <i>H</i>_c reaches the optimized value 3.12 T when the Tb content was 0.3 and is caused by the pinning field. By mixing light and heavy rare earths and optimizing the preparation process, this study stabilizes the crystal structure, enhances coercivity, reduces rare earth separation costs, and offers new insights for developing advanced permanent magnet materials.</p>