The Championship leaders were always the more dangerous side with some sprightly attacking play which often exposed a Birmingham side struggling to find some winning form.
In the first ever third round tie between the Midlands rivals Wolves' eager play was the major difference which was rewarded with two goals carved out by the highly rated Michael Kightly.
Referee Howard Webb was not without criticism from the home fans as he rejected a first-half penalty and was then involved in second goal when the ball bounced off him and put Wolves on to the attack from which Vokes notched his goal.
Birmingham, with only two goals from their last five games, obviously need the inclusion of their recent signings as once again their over-all performance was well below par.
One of the more pleasing aspects of Birmingham's early play was the confident start made by recent signing Robin Shroot. Only a month ago he was a £50 a match player with Harrow Borough in the Ryman Premier.
He quickly settled and produced several neat touches including a dangerous cross which had the Wolves defence in all sorts of trouble.
Surprisingly Wolves left their two leading marksmen, Sylvan Ebanks-Blake and Chris Iwelumo, on the bench but their attack was still more effective than the home side.
Instead, manager Mick McCarthy included George Friend for only his second start and he responded with Wolves' best chance after 15 minutes when the former Exeter left-sided player cleverly jinked his way through, only to have his close-range effort blocked by Maik Taylor.
For a spell the game was played in a haze as smoke swirled over the ground but it did little to put off either team in a period when Wolves, as expected, increased their attacking tempo.
This was emphasised in the 38th minute when they took the lead following a snappy move in which Kightly cleverly chipped a smart high pass into the path of the unmarked Keogh to ram his shot past Taylor.
Wolves survived an anxious moment when Richard Stearman slammed into Marcus Bent but referee Howard Webb was in close attendance and gave the benefit of doubt to the Molineux man.
Birmingham had trouble with Wolves' pacey attack as was demonstrated a minute before the break when goal-line clearances by Franck Queudrue and Liam Ridgewell in quick succession blocked shots from Vokes and the elusive Kighty.
Bent failed to re-appear for the second half following his earlier confrontation with Stearman but Birmingham still found themselves under pressure with Taylor keeping them in the game with a close-range save from Keogh.
But Keogh capitalised upon referee's Webb's assistance when he set up Kightly to produce another neat pass from which Vokes netted in the 51st minute.
Cameron Jerome went close to scoring when his 25-yard shot cannoned back off the crossbar, but Wolves survived to set up a meeting with Middlesbrough.