The visitors took a 28th-minute lead at the Estadio Jose Alvalade through Brazilian striker Deyverson.
Sporting's Peruvian attacker Andre Carrillo levelled matters six minutes later but that was as good as it got for the hosts.
Belenenses lie sixth - a point better off than Sporting, who had defender Jefferson sent off in stoppage time for a second bookable offence.
Rio Ave edged back ahead of Benfica at the top of the standings but lost their 100 per cent record as they were held to a draw at Moreirense.
Diego Lopes broke the deadlock for the away side with 28 minutes played but Moreirense - who now have five points from four outings - enjoyed an ideal start to the second period as Vitor Gomes restored parity.
Vitoria Guimaraes host Porto on Sunday and if there is a winner in that game Rio Ave will be dislodged.
Arouca picked up their first win of the campaign and were Saturday's only victors as Claro's fifth-minute opener proved enough to secure a surprise 1-0 triumph over Sporting Braga.