The Russian international, on loan from Chelsea, struck a glorious effort from long range eight minutes before the break in what was otherwise dull encounter at St Andrews.
Bolton's hopes of acquiring a much coveted Champions League place now appear to be fading and fixtures against the likes of Liverpool, Chelsea and Tottenham Hotspur are all still on the agenda over the next few weeks.
Despite their recent lack of confidence Birmingham stuck to their task even though their preparations took a massive blow early on as midfield pair Stephen Clemence and Nicky Butt had to leave the action after just half an hour in seperate incidents.
Wanderers had the first real sniff of goal in the 11th minute but in-form striker Kevin Davies could not get enough accuracy on his header following a cross by the roundly booed El-Hadji Diouf.
On 33 minutes substitute Mikael Forssell fired over at the other end a few minutes after coming on following some sloppy play by Bolton's young Irish international full back Joey O'Brien.
The only goal of the game came some four minutes later when the experienced Jarosik fired in his seventh of the season past Wanderers long serving goalkeeper Jussi Jaaskelainen.
Wanderers could have forced themselves back into the game on the stroke of half time but Maik Taylor in the Birmingham goal was at his very best to keep out a curling effort from Kevin Nolan.
The second half was unfortunately no better as far as Bolton where concerned as the Blues looked to consolidate their lead and gain a win which would pull them out of the drop zone for the first time in 2006.
Former Blackburn Rovers wide man Damien Johnson saw his cross cum shot tipped to safety by Jaaskelainen whilst Giannakopoulos stabbed wide at the other end after Kevin Davies had made a nuisance of himself in the opponents half.
Even the introductions of forward pair Jared Borgetti and Ricardo Vaz-Te could do little to spur Wanderers into forcing an equalising goal as the excellent Jermaine Pennant ran the show for Steve Bruce side.
Ironically Bolton's manager Sam Allardyce knows Pennant's attributes all too well having sold the often contraversial player to Arsenal from Notts County for a then English record £2 million fee for a teenager in the early part of 1999.
Forssell had a chance to double Birmingham's advantage late on but the Blues held on for a vital win which will put some pressure on their relegation rivals over the coming weeks.
Bolton on the other hand will be concerned about their run of defeats, the three losses in recent weeks is the worst run of form that the club has endured since their nightmare Christmas run in 2004.
A trip to Anfield to face European Champions Liverpool awaits on Saturday afternoon and this is followed by a home game against Premiership champions Chelsea on Saturday week.
Bolton Wanderers: Jussi Jaaskelainen, Joey O'Brien (Nicky Hunt), Tal Ben-Haim, Bruno N'Gotty, Henrik Pedersen, Abdoulaye Faye, Jay-Jay Okocha, Kevin Nolan (Ricardo Vaz-Te), El-Hadji Diouf (Jared Borgetti), Kevin Davies, Stelios Giannakopoulos
Subs Not Used: Ian Walker, Hidetoshi Nakata
Birmingham: Maik Taylor, Olivier Tebily, Kenny Cunningham, Martin Taylor, Mat Sadler, Jermaine Pennant, Stephen Clemence (Stan Lazaridis) (David Dunn), Nicky Butt (Mikael Forssell), Jiri Jarosik, Damien Johnson, Emile Heskey
Subs Not Used: Nico Vaesen, DJ Campbell
Referee:
Chris Foy
Attendance:
26,493
Booked:
Jermaine Pennant (Birmingham)
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