Gillingham clinched maximum points at Southend thanks to an early Chris Whelpdale strike.
Whelpdale had put the Gills ahead with three minutes gone and it proved to be the decisive goal at Roots Hall on Tuesday.
The Gills had the edge in the first half but had to defend in numbers after the break to keep Southend at bay.
Gillingham were keen to make amends for their previous outing, when they suffered a 1-0 defeat at home to Barnet and they did it with a win over Southend.
Martin Allen’s side made a dream start, against fourth-placed Southend, when Whelpdale side-footed home Joe Martin’s deep free-kick.
The Gills – backed by 1,184 travelling fans - dominated the first half but failed to make the most of their numerous chances and that left them always in danger to a more-than-capable Southend side.
There were five changes in the Gills starting XI with Adam Birchall being handed a first league start, while leading scorer Danny Kedwell was again on the bench, having only just passed a fitness test following a bout of illness.
Helping keep Southend out was debutant defender Leon Legge, who added real strength and experience to the back line, while also putting himself about in the opposite box during set-pieces.
Myles Weston, operating on the wing as boss Allen switched to a 4-4-2 formation, came close on several occasions, while former Southend stalwart Adam Barrett had a goalbound shot blocked.
Southend’s best chance of the first half came to Kevan Hurst but he smashed a shot wide with both Britt Assombalonga and former Gills striker Gavin Tomlin waiting for service in the middle.
Southend piled on the pressure just before the hour as Assombalonga had a chance deflected over and moments later Stuart Nelson made a diving save to deny Hurst.
The Gills were rattled and substitute Barry Corr should have equalised from a yard out, but with Matt Fish for company, he lost his composure and somehow put Tomlin’s cross over the bar.
Allen responded to the intense pressure by making a double switch, as both Charlie Lee and Danny Jackman came off the bench.
Southend eased off for a while but remained dangerous and Hurst sent a shot fizzing narrowly over.
The Gills were defending in numbers but had a rare chance with just over 10 minutes gone as Weston burst clear. He beat the defender and shot past the keeper but the effort bounced off the inside of the post and into the hands of the grateful goalkeeper.
Back at the other end Southend kept pushing for the equaliser and the Gills fans behind Nelson’s goal were thankful to see Ryan Cresswell head a good chance wide with seven minutes left.
In the final seconds of the game Joe Martin and Nelson combined to deny Corr as space opened up and he fired on target.
Gillingham: Nelson, Fish, Martin, Legge, Barrett, Payne, Frampton, Whelpdale (Lee 64mins), Weston, Birchall (Jackman 64mins), Burton (Kedwell 86mins). Subs not used: Forecast, Davies, Allen, Dack.
Southend: Smith, Clohessy, Cresswell, Timlin, Hurst, Prosser, Assombalonga (Eastwood 76mins), Tomlin, Barker, Laird (Corr 46mins), Mkandawire (Donnelly 80mins). Subs not used: Straker, Martin, Phillips, Bentley.
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