Striker Thabo Rakhale netted the only goal of the Group B clash two minutes from recess as the Buccaneers cruised to their second successive away win at the group stage and boost their chances.
It represents one of the lowest moments for Sfaxien, considered the most successful club in the history of the second-tier continental club with three triumphs.
With just a point from a maximum nine, the ‘Black and White’ have an arduous task in their quest to reach the knockout stage and had goalkeeper Rami Jeridi to thank for the narrow scoreline.
Sfaxien are yet to recover from the exodus of key players such as Fakhreddine Ben Youssef (Metz and now Esperance), Ferdjani Sassi (Metz), Boussam Boulabi (Hangzhou Greentown) and Gabonese Didier Ndong (Lorient), with Pirates having the better of the closely contested affair.
By the quarter-hour mark, Lehlohonolo Majoro and Thabo Matlaba had tested the Tunisians defence, but fail to convert with only Jeridi to beat on both occasions.
On 33 minutes, Sfaxien captain Ali Maaloul let in a shot from a free-kick that missed target to end the first half barren.
Two minutes after the break, Pirates went up through Rakhele, who dispossessed a Tunisian defender of the ball before chipping past onrushing Jeridi.
At the other end, Brighton Mhlongo was called to duty by saving Maher Hannachi’s grounder and parrying Maaloul’s effort from the rebound.
On the stroke of full time, Pirates broke loose on the counter but Sifiso Myeni saw his chip saved by Jeridi, only for substitute Kermit Erasmus to see his header from the rebound rattle the post.
The South Africans have six points, three shy of leaders Zamalek of Egypt. Leopards and Sfaxiex follow in that order with a point each.
25.07.2015 19H00 Al Ahly (Egypt) 1-0 Etoile du Sahel (Tunisia)
25.07.2015 19H45 Esperance (Tunisia) 1-2 Stade Malien (Mali)
26.07.2015 19H30 Zamalek (Egypt) 2-0 AC Leopards (Congo)
26.07.2015 20H30 CS Sfaxien (Tunisia) 0-1 Orlando Pirates (South Africa)
*All times are in local time