To investigate whether the presence of helium in apatite slows fission track (FT) annealing, we performed isothermal annealing experiments on large Durango apatite crystals in which we had created He-depleted rims and He-retaining cores. Single crystals were annealed at 310 °C under vacuum for 30–270 min to stimulate helium diffusion and damage annealing, after which spontaneous FT lengths were measured separately in rim and core regions. An unannealed control sample showed no rim–core length difference, indicating negligible geometric or etching bias. With increasing annealing duration, rim tracks shorten more than core tracks, and rim–core length distributions and means diverge significantly after ∼90 min. We interpret this rim–core contrast as evidence that helium impedes FT annealing, consistent with helium stabilization of defect structures known to occur in irradiated solids. These results imply that FT annealing kinetics is affected by helium content, with potential consequences for both apatite FT and (U–Th)/He thermochronometry.