Giroud headed home the only goal of the game on 65 minutes when the French striker got on the end of Theo Walcott's chipped free-kick.
The set-piece was awarded after Cheick Tiote had fouled Santi Cazorla, however, Pardew believes referee Lee Probert should have given his side a free-kick.
Pardew, though, acknowledged the decisions had gone in Newcastle's favour during Boxing Day's 5-1 victory over Stoke City and he was left frustrated by the manner of the goal his team conceded.
He said: "There was definitely a foul before then on [Vurnon] Anita, without a shadow of a doubt; there was a foul on [Moussa] Sissoko that he [referee Lee Probert] didn't give.
"In terms of the breaks of the decisions, I don't want to say the referee had a poor game, but sometimes he sees those calls and they go your way, sometimes they don't.
"Against Stoke, we had all the calls go our way and today, perhaps we were on the other side of it.
"It's just frustrating, a little bit, that we have not got something on the scoreboard in terms of a point, no more than that.
"One set-play where we didn't defend well has cost us and we have been good at them all year."