Jorginho netted another winning penalty to lift Chelsea to fifth in the Premier League table.
Mason Mount put them ahead three minutes before the interval at Bramall Lane.
Bottom side Sheffield United were gifted an equaliser by Antonio Rudiger’s farcical own goal early in the second half.
But the Blues’ lead was restored just three minutes later when Jorginho stepped up after Timo Werner had been brought down by keeper Aaron Ramsdale.
Werner’s drought continued but he was involved in both goals and worked tirelessly up front.
The opener was beautifully worked, with Werner exchanging passes with the recalled Ben Chilwell on the left and pulling the ball back for Mount, who fired into the bottom corner.
Chelsea seemed to be control when Oli McBurnie burst forward and played the ball into the area, where Rudiger bizarrely elected to lay it back to keeper Edouard Mendy but steered it past him and into his own net.
Rudiger’s blushes were spared when Jorginho, whose penalty clinched Thursday’s derby victory at Tottenham, calmly slotted home from the spot again.
Chelsea remain unbeaten under Thomas Tuchel, having won three of his four matches at the helm.
Chelsea: Mendy, Azpilicueta, Rudiger, Christensen, James, Jorginho, Kovacic, Chilwell (Alonso 62), Mount, Werner (Kante 75), Giroud (Hudson-Odoi 62).
Subs not used: Kepa, Abraham, Zouma, Ziyech, Gilmour, Emerson.