In fact, they were the better team over the 90 minutes and deserved their win over an out-of-touch home team.
Millwall, desperate for a result, dominated the first half and should have been more than one goal ahead at half-time.
Jay Simpson gave them the lead on 11 minutes when he flicked a neat pass from Jem Karacan into the corner of the net from six yards.
He should have had another three minutes later when another good Millwall move gave him a chance from near the penalty spot, but he sent the ball straight into the arms of keeper Arran Lee-Barrett.
Andy Monkhouse thought he had equalised for Pools on the half-hour, but he was offside as he slid the ball home after Antony Sweeney's neat back-heeled pass.
Just before half-time, Millwall again went close to doubling their lead, the impressive David Martin hammering a great shot from 20 yards against the underside of the bar before it bounced to safety.
After the break, Hartlepool came more into the game, but their finishing when chances came their way was as weak as the rest of their game.
Joel Porter headed over the bar from close range, Sweeney's shot was far too weak and easily saved by Rhys Evans, Willie Boland's low 20-yard shot was just off target and sub David Foley's late header never posed a problem for the Lions keeper.
Millwall based their performance on a lot of hard running and tigerish tackling to prevent Hartlepool hitting any kind of rhythm.
Martin led them well in midfield before being subbed in the second half and Karacan was always in the thick of the action at both ends of the pitch.