Terry Gornell was influential as Accrington beat Southend to pick up their eighth consecutive home win.
Ian Craney headed home Sean McConville's corner to give Stanley the lead, only for Ryan Hall to equalise with a fine free-kick after the break.
Gornell pounced to make it 2-1 when visiting keeper Glenn Morris flapped at Dean Winnard's throw-in.
Bilel Mohsni saw a second yellow for tripping Gornell in the box and Phil Edwards slotted in the penalty.
Accrington strengthened their play-off credentials and now sit in sixth place, two points clear of eighth-placed Gillingham.
Southend United manager Paul Sturrock told BBC Essex:
"This would be the most frustrating time I've had as football manager. I've had a team who in the middle of the season were flying high, winning games and on the front foot.
"Now we're at the stage in the season with injuries, tiredness and everything else.
"I'm having to chop and change every week, I'm getting no uniformity to the team and at the end of the day you get disjointed performances like we did again tonight."