<p>Deep coal–rock masses in complex geological environments often contain defects that threaten the long-term stability of engineering structures. To investigate the influence of defect shape on the creep behavior and failure mechanism of coal–rock, an improved creep model was developed by coupling the Kelvin–Voigt contact model with the parallel bond model in PFC. Based on calibrated mesoscopic parameters, simulations were performed on intact specimens and those containing rectangular, trapezoidal, inverted U-shaped, square, and circular cavities under stepwise loading. Results show that cavity defects significantly weaken the creep strength, strain, and elastic modulus of coal–rock, with degradation depending on cavity geometry. Rectangular cavities cause the largest drop in failure stress, inverted U-shaped cavities reduce the elastic modulus most, and square cavities lead to the greatest strain decrease. Under equal cavity areas, wider cavities promote greater compressive deformation. High-stress zones form and propagate differently across shapes: circular cavities generate symmetric stress fields and exhibit better structural stability, while other shapes develop stress zones outside the cavity that connect laterally. Cracks initiate in these high-stress regions and expand along stress paths, showing that cavity geometry dominates stress distribution and failure mode—rectangular and inverted U-shaped cavities favor local shear failure, whereas circular cavities tend toward global shear failure.</p>