The scoring was commenced in fine style when Spanish defender Ramis produced a stunning left-footed volley from Jean Beausejour's corner which rocketed past Jussi Jaaskelainen and into the roof of the net inside eight minutes.
Wigan's lead was doubled two minutes after the break when McArthur fired home Shaun Maloney's neat pass after the Scottish winger pounced on Jaaskelainen's poor clearance.
Wigan looked the more likely of the two sides to add to the goal tally but West Ham nicked one back late in the piece when Tomkins headed home George McCartney's cross but the damage had been done.
It was Wigan's first win in six Premier League outings as they moved to 15th place on the table with West Ham dropping to ninth.
DW Stadium, Wigan - 19,090