A commission spokesman said officials had investigated 24 appeals from losing candidates and voters before upholding results of the 10 February election in the Saudi Arabian capital.
The Riyadh vote was the first stage of nationwide municipal elections, part of the kingdom's tentative political reforms.
Elections were held a week ago in east and southern regions and the final stage will take place in April in the west and north.
"The commission discussed all the appeals presented to it and did not find anything that could be considered as having had an impact on the result of the election," the spokesman said in a statement carried by the official SPA news agency.
Losing candidates complained that the names of six of the seven winners in Riyadh appeared on a list circulated by mobile phone and the internet with the blessing of religious figures, a powerful influence in the conservative Muslim kingdom.
They said the Islamic endorsement of a group of candidates violated regulations forbidding coalitions or parties.
"The commission discussed all the appeals and did not find anything that could be considered as having had an impact on the result of the election"
Most of the victors won by a wide margin in each of the seven Riyadh districts, with one scoring six times more votes than his nearest rival.
The commission said it had seen no evidence that the seven successful candidates had formed any coalition or had sent the mobile phone messages.
Officials from the kingdom's sole mobile phone operator said the messages had been sent via an India-based firm, which
declined to say who was behind them.
The elections are being held for half of the seats on municipal councils. The remaining seats will be filled by government appointees. Women were barred from voting or standing in the elections.
The second round of voting in the eastern cities of Dammam, al-Khubar and Dhahran appeared to follow the pattern set in Riyadh, with seven candidates triumphing after their names were distributed on a list approved by 11 Sunni Muslim scholars.