Barry Corr's strike just before half time has pushed Southend United closer to a playoff place while dashing Fleetwood Town's faint hopes of automatic promotion from League Two as the sides go in level at the break.
The hosts were ahead late in the opening period when Steven Schumacher's curling free kick evaded everyone in penalty area and bounced inside the far post.
However, the Essex club were back on terms soon after when Corr headed home Ben Coker's cross.
Fleetwood were almost ahead again in the dying seconds of the half, but Mark Roberts's effort was just over the United crossbar.
Southend could seal a playoff place if they avoid defeat. If Fleetwood fail to win, both Rochdale and Scunthorpe United would be promoted to League One as it stands.