McManaman, on loan from Wigan, beat Royals keeper Adam Federici with a superb curling effort 10 minutes after half-time to hand the Tangerines all three points and inflict a first defeat in three Championship outings for Reading.
Blackpool had struggled in the opening 45 minutes, however, and Reading should have netted through any one of Adam Le Fondre, Hal Robson-Kanu or Jimmy Kebe - all of whom had good chances to open the scoring in the first period.
Both teams saw claims for penalties turned down over the course of the match, Blackpool for an apparent foul by Shaun Cummings on McManaman and Reading for a push on Alex Pearce, but in the end McManaman's strike proved to be the difference.
Le Fondre, restored to the Reading starting line-up in place of the injured Noel Hunt, had the first opportunity of the match - sending an ambitious overhead kick high over the Blackpool goal after four minutes.
The hosts quickly rallied, with Lomana LuaLua firing narrowly wide, as the match opened up at a frenetic pace.
The game's first flashpoint came just before the quarter-hour mark. McManaman was brought down by Shaun Cummings on the edge of the area and the Blackpool players wanted a penalty, only for referee Mark Brown to wave away the Tangerines' claims.
With home manager Ian Holloway still fuming on the sidelines, Blackpool almost found themselves behind moments later.
Cummings provided a pin-point cross and Le Fondre leapt at the back post to put a free header wide of the mark.
The Royals had another glorious opportunity to open the scoring almost immediately. This time winger Kebe failed to hit the target under pressure after he was played clean through on goal. And the visitors could have had their third goal inside the first 30 minutes when Robson-Kanu failed to connect onto Kebe's centre with the net gaping.
Blackpool, who had been pushed onto the back foot for much of the half, saw Ludovic Sylvestre's effort skid wide of the target after 31 minutes before LuaLua followed suit two minutes later.
Reading had the ball in the back of the net with 10 minutes remaining of the opening period through Simon Church, but the Welshman's celebrations were cut abruptly short by an offside flag.
Mr Brown turned down Royals shouts for a penalty after Pearce fell under pressure in the box, as the sides went into the interval goalless.
Blackpool got a foothold on proceedings in the early moments of the second half, and Gary Taylor-Fletcher might have done better when played through one-on-one with Federici, but the forward could not hand his side the advantage.
Federici had to be alert two minutes later to smother a loose ball in the area at the feet of Sylvestre.
However, Blackpool's pressure soon told and McManaman handed the hosts the advantage after 55 minutes. Matt Phillips slipped a neat pass into the feet of the on-loan Wigan man, and he ducked and dived inside before unleashing a curling effort which beat the outstretched Federici.
After spending much of the first period soaking up attack after attack from Reading, Blackpool were suddenly all over their guests.
Only Federici's fingertips prevented LuaLua from finding the back of the net from a tight angle, as Reading frantically tried to regroup.
McManaman tried his luck from the edge of the area without any reward after 69 minutes and Reading's only chance of any significance in the second half came with five minutes left - but Ian Harte sent his free-kick wide of the goal.