An extension of the attractive Hubbard model is constructed to study the critical behavior near a finite-temperature superconducting phase transition in two dimensions using the recently developed meron-cluster algorithm. Unlike previous calculations in the attractive Hubbard model which were limited to small lattices, the algorithm is used to study the critical behavior on lattices as large as (formula presented) These precise results show that a fermionic system can undergo a finite temperature phase transition whose critical behavior is well described by the predictions of Kosterlitz and Thouless almost three decades ago. In particular it is confirmed that the spatial winding number susceptibility obeys the well known predictions of finite size scaling for (formula presented) and up to logarithmic corrections the pair susceptibility scales as (formula presented) at large volumes with (formula presented) for (formula presented). © 2002 The American Physical Society.