An article of footwear has an upper that includes a knitted component and a sole structure secured to the upper. The knitted component may define a tube formed of unitary knit construction, and a strand may extend through a length of the tube. As another example, the knitted component may have a pair of at least partially coextensive knitted layers formed of unitary knit construction, and a plurality of floating yarns may extend between the knitted layers. In some configurations, the knit type or yarn type may vary in different regions of the knitted component to impart different properties. Additionally, the knitted component may incorporate a thermoplastic yarn that is fused in different regions of the knitted component to impart different properties. A flat knitting process or a variety of other knitting processes may be utilized to form the knitted component.