The Reds effectively put the game beyond Steve Spooner's side by the break as they hit four times in a first-half goal rush at Meadow Lane.
Ateef Konate struck after 14 minutes, with Will Swan making it two midway through the opening 45. Ollie Hammond then finished off another attack in the 34th minute ahead of Julian Larsson's smart finish 120 seconds from the interval.
Swan completed a brace and rounded off the scoring with a fine effort across goal on the hour mark during what was a tough night for the Birmingham City players.
Blues had to be alert from the word go as the hosts moved forward from kick-off and took their first shot on goal inside 15 seconds. As a result, Neil Etheridge was forced into an important early save and the 'keeper again had to be on the ball to sweep up an under-hit back pass soon after.
In response, Remi Walker had two efforts well saved by opposition 'keeper Nicky Hogarth, first seeing a free-kick pushed around the post and then an effort from open play shovelled away from danger.
However, it was Forest who broke the deadlock after 14 minutes. Konate was able to get a shot off outside the area and found the corner via a deflection that cruelly deceived everyone on the away side.
The home team thought they had added a second when Swan rounded Etheridge and slid the ball towards goal, but Captain Mitchell Roberts smelt the danger and mopped up from underneath his own crossbar.
Despite this intervention, an extension to the lead soon came when Swan tapped home at the far post from a perfectly placed Larsson cross.
The reaction from Blues was to gather themselves, putting together a sustained spell of possession, and a half-chance was created when Jordan James flicked a set-piece into a dangerous area.
But consistent with the attacking pattern in Nottinghamshire, Forest sprung another flowing move to add goal number three. Swan turned provider to lay on an assist with a simple square pass that allowed Hammond to roll the ball into an empty net.
Unfortunately, the half-time whistle did not come without any further concession as Andy Reid's men added a fourth shortly before the recess. Larsson burst into the penalty box on the angle and lifted his finish high into the net at the near post.
Just two minutes after the restart, Josh Williams had a shot well blocked as Blues endeavoured to take something from their trip to the East Midlands.
Instead, it was Forest who had more reason for cheer as Swan made his a double two thirds into the contest. The number nine was slipped through by Fin Back and made no mistake as he rifled in.
Spooner introduced Caolan Boyd-Munce, Kyle Hurst and Yoane Zahore and their introductions all coincided with a stemming of the Forest goals as his side refused to give in.
In fact, the game was concluded with the defeated but not entirely disheartened Blues on the attack. Jordan Graham's inch-perfect cross was met well by the head of Walker, only for Hogarth to spear it over the bar.
Nottingham Forest: Nicky Hogarth, Fin Back (Rezart Rama 70, Aaron Donnelly, Tyrese Fornah (captain), Baba Fernandes, Sam Sanders, Billy Fewster (Josh Barnes 61), Ollie Hammond, Will Swan (Lewis Salmon 66), Julian Larsson, Ateef Konate.
Substitutes not used: Aaron Bott, Joe Gardner.
Booking: Sanders 31, Salmon 85, Hammond 90.
Blues (4-2-3-1): Neil Etheridge, Marcel Oakley, Tommy Fogarty, Mitchell Roberts (captain), Juan Castillo, Alfie Chang, Remi Walker, Josh Williams (Caolan Boyd-Munce 63), Jordan James (Kyle Hurst 63), Jordan Graham, Leo Dos Reis (Yohane Zohore 81).
Substitutes not used: Oliver Basey, Cianole Nguepissi.