The former monopoly, which competes domestically with Etihad Etisalat (Mobily) and Zain Saudi, made a net profit of 2.15 billion riyals ($573.2 million) in the three months to Sept. 30.
This compares with a profit of 2.32 billion riyals in the prior-year period, a bourse statement said.
Six analysts polled by Reuters had on average forecast STC, which owns stakes in operators in the Gulf, Turkey and Asia, would make a quarterly profit of 2.16 billion riyals.
STC had reported falling profits in seven of the preceding eight quarters, stalling an improvement in its bottom line that had been sparked by the operator trimming its international ambitions and refocusing on its lucrative home market.