Blues suffer first defeat of the 2019/20 league campaign.BCFC
Their hosts showed a clinical edge that Blues couldn't muster.
Forest scored twice in seven first-half minutes through Joe Lolley (15) and Lewis Grabban (22), and that effectively killed the contest off.
For all their earnest effort, possession and probing, Blues were unable to really cause enough moments of danger to make it uneasy for Forest.
Michael Dawson (65) added a third from a corner and that was that for Blues, who had little left to play for but pride as Forest looked to pick them off on the break.
After a decent start Blues - who made the early running and forced a couple of corners - were caught napping in the 15th minute, from a
free-kick that was conceded by a late challenge from Ivan Sunjic, at a second phase from a cleared Forest flag-kick.
Lolley scored from similar range in similar circumstances last season in the corresponding game and Blues simply weren't switched on to the possibilities.
Forest took the free-kick quick and short, to Lolley to dribble forward. He then duly tried his luck from long range and although Lee Camp got a hand to his low, skidding shot, it found the back of the net.
It came as a crushing blow to Blues, who kept an unchanged starting line-up, and undid their bright beginning.
And then it got worse, seven minutes later, when Forest doubled their lead.
Lolley attacked down the right and got towards the byline before standing up and inviting cross to the far post.
Grabban climbed highest and directed a downward header back the way the ball came and inside the near post, despite Marc Roberts best efforts to clear from the line.
A quarter through the game, two attacks of any substance from Forest and Blues were already up against it.
Camp was next called into action when Sammy Ameobi sprinted away from Maxime Colin and fashioned a shooting chance, at a tight angle, in the box, which the 'keeper parried away at the front stick.
Dan Crowley tried his luck with a searching attempt from 25 yards that cleared the crossbar before Sunjic, with a hitch volley after a corner was cleared, also had a pop, from outside the box.
But Forest were comfortable with such an advantage accrued in double quick time.
Blues spurned a good opening, gifted by Aro Muric's poor clearance, that came straight at David Davis. He moved the ball to his right for Gary Gardner, who was in space near the edge of the area.
As Lukas Jutkiewicz moved free into position on the far side of the box, Gardner was caught in two minds and his eventual shot sailed harmlessly over the woodwork.
As at the start of the match, Blues made most of the running as the half drew to a close (they had more shots and more corners) but couldn't discover that telling end product required.
Half-time: Forest 2 Blues 0
In the opening 10 minutes or so of the second-half Blues had all of the possession and play, and Forest were just sitting in.
Jutkiewicz almost got on the end of an inswinging cross by Roberts after a corner, but good strength from the covering Ameobi ensured he couldn't get anything on it.
A change was made with Alvaro Gimenez replacing Gary Gardner for his Blues debut on the hour. Crowley, who was playing off Jutkiewicz, moved wide right, allowing Gimenez to go up top.
Forest, with Grabban as an outlet to go in behind, woke from their slumber with a long ball to the striker and after he brought others into play and the ball was crossed low, a clearance came straight out to Jack Robinson, whose shot from a close angle was blocked by a combination of Roberts and Harlee Dean.
And from the corner Forest promptly scored their third, Dawson steaming in to powerfully glance past Camp from inside the six-yard box (65 minutes).
Forest had done nothing to that moment, but Blues hadn't been able to trouble them, and they scored again from the first attack of the second period.
Forest then could have scored a couple more as Blues rocked, Samba Sow nodding down from close range after a ball was crossed in from the right.
Gimenez and Jutkiewicz almost combined nicely but for the latter having the ball taken off his toes as he was about to shoot inside the Forest area.
Not surprisingly as Blues strived to get something, more space began to appear and Ameobi missed an absolute sitter from just outside the six-yard box after a raid down the right, from which he was teed-up by Tiaga Silva.
Next Grabban, free in the area, glanced wide from a glorious position as Albert Adomah picked him out from the left.
Blues kept going until the end but it was a bad day at the office, without a doubt.
Forest (4-1-4-1): Muric, Cash, Robinson, Dawson, Worrall, Watson, Sow (Adomah 72), Semedo (Silva 57), Ameobi (Mir 79), Grabban, Lolley. Subs not used: Samba, Ribeiro, Figueiredo, Jenkinson.
Goals: Lolley (15), Grabban (22), Dawson (65).
Blues (4-4-2): Camp, Colin, Pedersen, Dean, Roberts, Gary Gardner (Gimenez 60), Sunjic, Davis, Villalba, Crowley (Seddon 90), Jutkiewicz. Subs not used: Stockdale, Harding, Craig Gardner, Clarke-Salter, Medina.
Booked: Sunjic (15), Gimenez (63).
Referee: T Harrington
Attendance: 27,281 (away 1,995).