Nicky Bailey struck in the 72nd minute and substitute Steve Morison 90 seconds later as the Lions came from behind to inflict Blackpool's first defeat of the Championship campaign and knock them off top spot.
It looked like being the same old story for Millwall and Lomas, who faced calls for him to be sacked during the 5-1 home mauling by Derby on Saturday, after Tom Ince gave Blackpool the lead.
But Liam Trotter equalised from the penalty spot in first-half stoppage time and Bailey and Morison finished the job after the break to ease the pressure on their beleaguered boss.
The former West Ham captain, appointed in the summer following Kenny Jackett's resignation, made six changes to his side following the Derby drubbing.
One of them, Leicester loanee Martyn Waghorn, was the liveliest performer in the opening stages and he tested Matt Gilks from 20 yards with a swerving shot.
But, totally against the run of play, Blackpool took the lead in the 16th minute through Ince's third goal of the season.
Mark Beevers' poor defensive header fell straight to the England Under-21 midfielder and he drove the ball through a crowd of players and into the net.
Lomas' luck was out at the other end moments later when Waghorn's cross was met by a glancing header from Martyn Woolford which beat Gilks but came back off the far post.
But Millwall were gifted a way back into the match in first-half stoppage time when Blackpool failed to deal with a free-kick from Woolford.
Trotter took a swing and a miss in the area and, as Jimmy Abdou attempted to take control of the loose ball, the grounded Isaiah Osbourne stuck out a hand and knocked it out of the midfielder's path.
There was a lengthy delay as Blackpool's players protested but Trotter held his nerve to calmly send Gilks the wrong way.
It was all Millwall after the break and their pressure was rewarded when Woolford swung over a corner and Bailey stole in at the far post to volley into the roof of the net.
Throwing away the lead became a feature of Millwall at home last season, but for once there was no time for the nerves to kick in.
Morison raced on to a ball over the top before beating Gilks with a fierce shot to seal a much-needed win - only their second at The Den in the league since New Year's Day.