The relationship between polycentric urban structure and urban amenities is examined across 380 U.S. Metropolitan Statistical Areas (MSAs). Polycentricity indices are developed using population density distribution, and amenities from the Overture Maps database are categorized into comparison, convenient, leisure, and catering types. After controlling for socioeconomic, land use, and street network factors, higher polycentricity is found to be associated with greater quantity and more even spatial distribution of amenities—but lower diversity across categories. Stratified analysis shows that this inverse relationship with diversity exists only in large and medium MSAs, while small MSAs exhibit greater diversity under polycentric structures. This may reflect functional specialization in larger MSAs versus multifunctional centers in smaller ones. For per capita amenity indicator, amenities in polycentric MSAs are more balanced distributed. These findings highlight the nuanced impacts of urban structure on amenity provision and offer insights for urban planning.