It curves to the east-northeast and finally enters Atlanta proper, on the Adamsville–Old Gordon neighborhood line in the western part of the city. At a bridge over SR 139, the highway begins traveling along the Adamsville–Fairburn Heights neighborhood line. After passing Collier Heights Park, it curves to the southeast and has an interchange with I-285 (Atlanta Bypass). This interchange is just south of the Basoline E. Usher Elementary School and on the southwestern edge of Harwell Heights Park. Right after the I-285 interchange, the highway briefly travels on the Westhaven–Collier Heights neighborhood line. It crosses over Sandy Creek and then has an interchange with SR 280 (Holmes Drive). At this interchange, it begins to briefly travel on the Westhaven–Dixie Hills neighborhood line. Just southeast of this interchange, it travels along the Florida Heights–Dixie Hills neighborhood line. At a crossing of Fairfield Place NW, I-20 begins to parallel SR 139. Just north of Westview Cemetery, it travels along the southern edge of the Penelope Neighbors neighborhood. The highway curves to the east-northeast and has an interchange with Martin Luther King Jr. Drive. It immediately curves back to the southeast and begins to travel along the southern edge of the Mozley Park neighborhood. Upon traveling under a bridge that carries Westview Drive SW, it begins traveling along the Westview–Mozley Park neighborhood line. Upon reaching a partial interchange with Langhorn Street SW, which is only accessible from the westbound lanes, it enters the West End neighborhood. Upon crossing over Lawton Street SW, it begins to briefly travel on the West End–Harris Chiles neighborhood line. The interstate curves to the east-southeast and has an interchange with Lowery Boulevard. It passes The Mall West End at a partial interchange with Lee Street, which is only accessible from the westbound lanes. At this interchange, I-20 begins to very briefly travel along the West End–Atlanta University Center neighborhood line. Upon crossing over US 29/SR 14/SR 154, it briefly travels through the Adair Park neighborhood. Upon crossing over US 19/US 41/SR 3, the highway slips through the northern part of the Pittsburgh neighborhood. It curves to the northeast and – almost immediately – enters the Mechanicsville neighborhood. It has an interchange with McDaniel Street SW that leads to US 19/US 29. At this interchange, it begins to travel along the Mechanicsville–Castleberry Hill neighborhood line.