After leaving the concurrency with SH 11, Bus. SH 121-D runs north and northeast before ending at an intersection with SH 121. Business State Highway 121-H (Bus. SH 121-H) is a business route of SH 121 that serves the town of Lewisville. The highway was designated in 1999 when SH 121 was re-routed around the city. SH 121-H begins at an interchange with SH 121/Sam Rayburn Tollway in Coppell. The highway runs northeast through industrial areas of Lewisville and turns to the north at an interchange with FM 3040 (Round Grove Road)/Denton Tap Road. Bus. North of here, SH 121-H runs by many residential areas before meeting I-35E. North of I-35E, the highway runs just south of the city's central business district and turns in a northeast direction. At Main Street, Bus. SH 121-H turns in a more eastern direction and crosses over the Elm Fork Trinity River. The highway continues to run east and meets FM 544 at an intersection before ending at an interchange with SH 121/Sam Rayburn Tollway.