Clinical experience suggests that overlapping coronary stents result in an increased in‐stent restenosis. This study investigates the underlying mechanisms in a porcine coronary model. Single or two overlapping self‐made stainless steel single wire sinusoidal helical coil stents were randomly deployed in the right coronary artery of 20 cross‐bred pigs. The pigs underwent a control angiogram at 6 weeks and were then sacrificed. Quantitative coronary analysis before, immediately after stent implantation, and at 6 weeks was performed using the semiautomated Polytron 1000 system. Morphometry was performed using a computerized morphometric program. Angiographic analysis revealed a decreased recoil in the overlapping group (1% vs 4%: P < 0.02) and a significantly larger minimal stent lumen diameter at follow‐up in the single stent group (2.87 ± 0.16 vs 2.58 ± 0.22 mm, P = 0.005). Histopathology showed a significantly increased injury (1.27 ± 0.43 vs 0.83 ± 0.44, P = 0.042) and inflammatory reaction (1.51 ± 0.11 vs 1.09 ± 0.54, P = 0.035) surrounding the stent filaments in the overlapping stent group. Morphometric analysis showed a significantly higher neointimal hyperplasia (3.34 ± 0.68 vs 2.16 ± 1.48 mm2, P = 0.034) in the overlapping stent group. Overlapping stents result in a more pronounced coronary vessel injury resulting in more inflammation and neointimal hyperplasia compared to single stents.