This study explores the bubble nucleation process and heat transfer characteristics on nanostructured solid surfaces with mixed-wettable pillars using molecular dynamics simulations. Five different surfaces were designed by varying the wettability of the central pillars while keeping the lateral pillars hydrophilic. The nucleation behavior of argon bubbles was observed to differ significantly across these surfaces due to the combined effects of nanostructuring and mixed wettability. On surfaces with hydrophilic central pillars, bubble nuclei primarily formed above the pillars, with minimal nucleation among them, owing to strong argon adsorption and molecular layering that require higher temperatures for nucleation initiation. As the central pillars became less hydrophilic, nucleation among the pillars increased. In contrast, surfaces with hydrophobic central pillars exhibited distinctive nucleation patterns, including the presence of stable bubbles among the pillars even before heating commenced. Measurements of bubble volume, argon density, potential energy, and heat flux revealed that increasing the hydrophobicity of the central pillars promotes bubble nucleation within the pillar regions, alters bubble growth dynamics, reduces argon density among the pillars, and affects heat transfer rates. These findings provide valuable insights into how pillar wettability influences bubble formation and growth, suggesting that engineered surfaces with mixed wettability can be designed to control bubble dynamics and enhance heat transfer performance in applications involving phase change and thermal management.