They had Yong Kuong Yong to thank for the victory, as the striker scored in both halves to secure the win.
The KL striker collected a pass from Badrul Hisyam and went past his marker to plant an accurate shot into the far corner in the 27th minute, but was left frustrated at the end of the first half as Nor Fazly Alias equalised for the visitors to leave the score tied at 1-1.
Kuala Lumpur came out in the second half fighting, with Kuong Yong scoring the winning goal with a well-hit header. T-Team made frantic attempts to regain momentum, but were foiled by a stubborn KL defence, who held out for the win.
Elsewhere in Group D, Selangor managed a 2-0 victory over PDRM at the Shah Alam Stadium.
Group A saw Kedah fall to a 2-1 loss to Sabah, and Perak snatch a 2-1 win over Johor at the Perak Stadium in Ipoh.
In Group B, Trengganu enjoyed a 3-2 victory over Selangor PKNS, and Negeri Sembilan thumped Kuala Lumpur, Sime Darby 5-0 in the Tuanku Abdul Rahman Stadium.
Group C saw Kelantan beat Johor FC 2-1, and Kuala Lumpur Felda United FC triumph 1-0 over Sarawak at Kelana Jaya.
Kedah 1-2 Sabah
Perak 2-1 Johor
Terengganu 3-2 Selangor
Negeri Sembilan 5-0 Kuala Lumpur, Sime Darby
Kelatan 2-1 Johor FC
Kuala Lumpur Felda United FC 1-0 Sarawak
Selangor 2-1 PDRM
Kuala Lumpur 2-1 Terengganu PBDKT T-Team