Plymouth started the brighter of the two sides, and, after forcing four early corners, Stevie Crawford shot narrowly wide after dispossessing Rufus Brevett.
Matthew Etherington volleyed wide before supplying a pinpoint cross for Marlon Harewood; he lashed home from close range but the linesman, signalling offside, cut short West Ham's celebrations.
Bobby Zamora was then booked for jumping into Graham Coughlan, David Norris received a yellow card for a late challenge on Brevett, and David Worrell was cautioned for holding on to the ball when West Ham had a free kick.
West Ham took the lead just before the break when Steve Lomas applied a glancing header to a Bobby Zamora cross to score his first goal in two seasons.
Worrell blazed over before crossing for Norris - his close range header was tipped brilliantly over the bar.
At the other end, Matthew Etherington hit a first time shot that was saved by Romain Larrieu after Zamora headed on a Tomas Repka free kick.
Bywater had to be alert again when Mickey Evans headed a Lee Makel cross goal bound at close range, and again he tipped over for a corner.
Lee Hodges was booked for a foul on Nigel Reo-Coker and Harewood followed for querying a linesman's decision.
Paul Wotton, who had just replaced Hodges, then struck a blistering free kick past the West Ham wall that Steve Bywater couldn't keep out, despite getting a hand to it.
Don Hutchison, who had not been allowed to go out on loan last week due to an injury to Sergei Rebrov, replaced Zamora.
Steve Bywater was restored to the starting line-up at the expense of James Walker, while Carl Fletcher came in for Adam Nowland and Anton Ferdinand made way for Calum Davenport.
TEAM: Bywater, Repka, Brevett, Davenport, Mullins, Lomas, Fletcher, Reo-Coker, Etherington, Zamora [Hutchison], Harewood.
Subs unused: Walker, Powell, Ferdinand, Chadwick.