Saphir Taider's early opener proved enough to earn Stefano Pioli's men back-to-back victories for the first time this season, following Tuesday's win over Fiorentina, with Alessandro Diamanti making the points safe midway through the second half.
Francesco Pisano's red card followed a careless tackle and saw the Sardinians reduced to 10 men before substitute Cristian Pasquato added gloss to the scoreline as Bologna opened an 11-point gap on the bottom three.
Taider exchanged quick passes with Alberto Gilardino before slotting the ball beyond Michael Agazzi inside five minutes at the Dall'Ara.
That early boost carried the hosts through a fine period leading up to the second goal, with Gilardino testing Agazzi three times thanks to the creativity of Archimede Morleo.
Diamanti needed no help to find the goal in the 18th minute, though, and the former West Ham striker twisted a superb left-footed drive into the top corner.
Marco Sau threatened to drag Cagliari back into the game with a searing shot on the volley, but the ball sailed harmlessly wide as Bologna wrested back control.
Gilardino missed a clear chance to make it 3-0 on the half-hour mark as he waited too long to strike the ball with Agazzi off his line.
To their credit, Cagliari ensured there was a contest to return to after the break when Agazzi produced a solid save to deny the marauding Gilardino.
Panagiotis Kone was the next man to test Agazzi, the Greek midfielder heading a Diamanti cross just wide of the target, and Manolo Gabbiadini soon tried his luck with a searing strike from distance.
Cagliari made life easier for their hosts in the 57th minute as Pisano left them a man light in defence by going in high on Morleo with his outstretched leg.
The extra space helped Taider find Gilardino in good space in the box, but Agazzi raced out to block, and home substitute Davide Moscardelli could only win a corner with a promising strike.
Bologna retained control of proceedings as time ticked away and any hope of a late Cagliari comeback was extinguished when Daniele Conti withdrew injured, with all his side's substitutes already in play.
That gave Pasquato more than enough space and time to inflict more misery on the Sardinians with a swerving shot from distance that nestled in the back of the net.