The order-disorder transition temperature of the PtCo bulk alloy and the effect of heat treatment on an as-sputtered disordered PtCo thin film have been investigated using Monte Carlo simulations coupled with a modified embedded atom method. From the long-range order curve combined with atomistic configurations, the order-disorder transition temperature is estimated between 1000 K and 1200 K. It has also been confirmed that the heat treatment at 900 K on the as-sputtered PtCo thin film induced ordering. The Pt segregation at the top surface of the thin film resulted in ordering of the whole thin film, except for four or five bottom layers probably because of the influence of the substrate.