After recovering from a hernia operation, Scottish full-back Tierney made his Gunners debut in the 5-0 win over Nottingham Forest in the Carabao Cup third round on Tuesday, a game in which Martinelli scored twice.
Holding also found the net and said: “Kieran's a good Scottish lad who brings a bit of banter to the team.
"He and I are getting on really well, you couldn't ask for a better way for him to settle in.
“He's a top-quality lad and he's a great lift in the changing room as well. He's a really nice guy and I'm so happy for him to play and get 60 minutes under his belt."
On Martinelli, he added: “He's been a handful in training. He's a sharp lad and a natural finisher.
“You saw the header, he's a small lad and he got up there and won it. He's impressive so hopefully he can continue with that."