Man of the Match Bernard Parker got the goal for the Soweto giants, who had goalkeeper Itumeleng Khune sent off late on by referee Phillip Tinyane at Peter Mokaba Stadium.
The result saw Chiefs extend their lead at the Absa Premiership summit to 10 points with five games left, while Usuthu remain two points behind fellow strugglers Moroka Swallows and Free State Stars, but having contested an extra fixture.
Doctor Khumalo notably supervised the Amakhosi bench as head coach Stuart Baxter served the first instalment of a two-game ban following his dismissal in the Nedbank Cup loss to Black Leopards last month.
The hosts took the initiative in the 17th minute, as Parker exchanged passes with Siphiwe Tshabalala on the edge of the penalty area before stepping past the challenge of Mbulelo Mabizela and firing home a low, left-footed shot.
The Glamour Boys came close to doubling their lead soon after but George Lebese's stunning volley was denied by the woodwork.
At the other end, Thabiso Dlamini triggered a good save from Itumeleng Khune with a long-range strike midway through the opening stanza.
The second period delivered little in the way of goal-mouth action, with Chiefs substitute Matthew Rusike flashing an acrobatic attempt wide of the target in the latter stages.
The home side were forced to play out the final seven minutes with ten men after Khune received two cautions in quick succession for time-wasting and dissent respectively, prompting the introduction of Reyaad Pieterse at the expense of Lebese.