A David Cotterill special proved the difference as Blues recorded a fine away victory at Huddersfield Town.
The Wales international delivered a stunning free-kick in the 70th minute that beat Alex Smithies all ends up. The ball swerved viciously after Cotterill lashed it at goal from just outside the penalty area and it was simply too hot to handle for the Huddersfield 'keeper.
Cotterill's strike was just reward for an improved second-half from Blues, who were on the end of a few choice words from Gary Rowett at the break.
Blues performed with much more tempo, purpose and their wide players Cotterill and Demarai Gray were threatening in the second-half.
That said, there was a huge scare for Blues deep in stoppage-time when Huddersfield threw caution to the wind in search of an equaliser.
From the right wing corner, the ball screwed its way to the far post and Anthony Gerrard, who just needed to thump it in.But he got his feet mixed up and the ball ended going behind him, allowing Blues to clear.
Had that chance gone in it would have been harsh on Blues, who fielded an unchanged starting side once more.
The first-half was a scrappy affair and apart from a David Davis attempt that went wide, Blues didn't really get Smithies worked up.
In the 40th minute, a Lee Peltier cross from the right was scuffed by Sean Scannell but found its way through to the far post where Grant Holt hammered it at goal but Randolph spread himself brilliantly to keep the attempt out and ensure the sides went into half-time locked at 0-0.
Blues were a different proposition in the second period, aided by a slight midfield change by Rowett.
Smithies punched away a dangerous Gray cross as Clayton Donaldson seemed to be dragged down by Mark Hudson and Blues, firmly on the front foot and getting Andy Shinnie much more involved, dictated proceedings.
The goal came after Huddersfield gave the ball away deep in their own territory. Donaldson went to go past Gerrard and he cynically stepped across to halt his progress into the area. Cotterill then did the rest with one of those trademark blasts.
Huddersfield sent on Nahki Wells and James Vaughan and to test Blues, who remained strong and focused.
Callum Reilly and Lee Novak were put into the fray to help Blues ensure there were no gaps for the hosts to exploit.
Randolph made a good, tip-away save from Joe Lolley as time ticked down. And then there was the frenetic scramble in the fifth minute of added-time, Gerrard fluffing his chance.
Blues victory lifted them further away from the Championship danger zone and, in fact, left everyone with half an eye on matters further above them.
Huddersfield had not lost on their own patch since September and under Rowett Blues have now won five of their eight matches, with two drawn.