Envelopes had allegedly been sent for counting without the seal of the National Vote Counting Commission in 31 of the 34 departments in the country, a violation of electoral law.
The Constitutional Court is expected to reach a decision on the appeal on Monday.
Dieng came in third with 14.9 per cent of votes in the February 25 election.
Wade received 1.9 million of the 3.4 million valid votes cast, or 55.9 per cent, according to the National Vote Counting Commission.
Senegal is widely regarded as a bastion of democracy in volatile West Africa.
Ecowas, West Africa's regional election monitor, said the election was sufficiently free and fair but Reporters Sans Frontieres, a Paris-based media watchdog, said Wade's campaign was given overwhelming coverage by state media.