Abstract We use noncontact atomic force microscopy (AFM) as well as scanning tunneling microscopy (STM) to investigate the mechanical properties of quasi-one-dimensional indium chains on an In/Si(111) surface. The system shows phase transition from the 4×1 to 8×2 periodicity at temperatures near 120 K. AFM could not detect ×2 modulation along the chains near point defects at room temperature, but STM could. In contrast, the 8×2 phase at 80 K could be observed by AFM in phase with the STM image. High-resolution AFM images show that the 8×2 phase is not perturbed by mechanical interaction with the AFM tip because of misalignment between the reaction coordinates of the phase transition and the direction of the vertical force of the tip.