The Shrimpers top-scorer struck four minutes from time to salvage a late point after Stoke looked to be cruising thanks to a first-half Ricardo Fuller strike.
Stoke thought they were right back amongst the play-off pack before Eastwood's last-gasp strike gave his relegation battlers a share of the spoils to leave them four points from safety.
Stoke's last outing, a goalless bore-draw against Ipswich Town, rests in the memory more for the return of fan-favourite Lee Hendrie than its standard of football.
And it only took the Aston Villa loanee, signing on for his second stint with the club, 15 minutes to make an impression in this one.
The well-liked wing-man dropped a crafty ball around the visiting rearguard for Ricardo Fuller to somehow smash over with the goal left at his mercy.
But the Britannia Stadium wasn't forced to wait much longer for the deadlock to be broken - a move instigated by another transfer-deadline-day signing.
Temporary incumbent Jonathan Fortune, replacing outgoing Stoke stalwart Michael Duberry, arrowed a ball over for Fuller, via a Mamady Sidibe nod-on, which the striker gobbled up.
The City top-scorer put his wasteful recent run behind him and finished off his seventh of the season with gusto - hammering past the helpless Darryl Flahavan.
Sidibe should have doubled City's half-time tally but instead the Potteries outfit entered the dressing room fuming following a succession of dubious decisions from referee Anthony Taylor.
The whistle-happy Cheshire official left the field to a chorus of jeers after Stoke's attempts to substitute injured Andy Griffin were ignored - forcing City to conclude the half a man light.
But despite Taylor's claims to be the villain of the piece, Sidibe's wastefulness in front of goal was drawing its own share of disgruntled murmurs from the home-support.
The Mali international's credibility as a striker was again being questioned after he repeated the amazing feat of ballooning from point-blank range twice in two games.
City began to assert a real hold on the game in the second half and conducted a relentless assault on the Shrimpers goal - Hendrie leading the charge.
The impressive former England international first nodded over from Fuller's centre before forcing Flahavan to tip over a blistering cross-cum-shot.
But Southend had been saving a hammer-blow and it came at the death via usual suspect Eastwood.
The hosts' back-line let the Southend top-scorer wander in through the back-door to tap in Richie Foran's low cross at the back post.