In Texas, the road runs south-north for 471.3 miles (758.5 km) from the International border with Mexico to the Oklahoma state line north of Gainesville.

Here, US 77 begins its overlap with I-35 that lasts until Hillsboro, where the highway then parallels I-35E until Red Oak.

North of Red Oak, US 77 overlaps I-35E through Dallas, leaving the interstate again in Denton.

In Denton, US 77 is a suburban road that serves the downtown area and has an overlap with US 377 in the town, intersecting US 380 near Texas Women's University.

In 1943, the highway was extended south of Corpus Christi to the international border at Brownsville; this extension also rerouted the section of highway between Sinton and Corpus Christi, as the previous route traveled through Gregory between the two towns.

[2] The section of highway through Victoria was rerouted in 1978 to remove a concurrency with US 59, but this was cancelled the following year.

In 1997, US 77 was extended so the highway's official designation ran to the Los Tomates International Bridge in Brownsville.

In 2003, the section of US 77 in Robstown between FM 892 and 9th Street was removed the state highway system as construction of a bypass around the town began.

[3] An official ceremony was held on December 5, 2011 to unveil I-69 signs on the Robstown-Corpus Christi freeway.

The section of freeway in the East Rio Grande Valley received approval for Interstate designation in May 2013.

South of Corpus Christi, US 77 is a freeway around most of Kingsville, with interchanges being constructed at US 77 Bus.

A freeway section of US 77 also exists in the town of Bishop, with a bypass of Driscoll recently finishing construction, with the northbound lanes opened to traffic in 2021 while the southbound lanes opened in August 2023; making the freeway complete from I-37 to Kingsville.

[8] Between Corpus Christi and Victoria, US 77 is still mostly a divided highway that does not bypass most of the towns it travels through.

US 77 has nine designated business loops in Texas, between the one in Waco and the mainline highway's southern terminus at the Mexico border.

US 77, which is a 91-mile (146 km) alternate route of US 77, located entirely in the state of Texas, running from Hallettsville to Refugio.

The business loop begins at an interchange with US 77 southwest of Sinton, turning northeast before intersecting with US 181 and SH 188.

The southern terminus of the business loop begins at an interchange with I-69E/US 77 and travels northeast into town, with the only major intersection being FM 665.

The business loop runs mostly parallel with the mainline I-69E/US 77 and its northern terminus is at another interchange with the latter highway.Business U.S. Highway 77-V (Bus.

The business loop's southern terminus begins at an intersection with US 77 and travels northwest and then turns to the north, eventually entering Kingsville.

US 77-V then turns back to the northeast after leaving Kingsville and eventually enters Bishop after a few miles.

The business loop continues northeastward before reaching an intersection with Willacy County Road 3690W.

The business loop begins at an interchange with I-69E and US 77, heading northwest through San Benito before entering Harlingen.

After leaving Combes, the business loop reaches its northern terminus at another intersection with I-69E and US 77.Business U.S. Highway 77-Z (Bus.

The loop's southern terminus begins at an intersection of SH 4 and takes a northwestern direction before turning to the north.