By the beginning of August, "Astoria" had been reassigned to Task Group 62.3 (TG 62.3), Fire Support Group L, to cover the Guadalcanal-Tulagi landings. Early on the morning of 7 August, the heavy cruiser entered the waters between Guadalcanal and Florida Islands in the southern Solomons. Throughout the day, she supported the Marines as they landed on Guadalcanal and several smaller islands nearby. The Japanese launched air counterattacks on the 7th–8th, and "Astoria" helped to defend the transports from those attacks.