The 45-year-old actor announced his wife was pregnant with their second child together in an adorable video on Instagram.
He is also dad to 12-year-old Coco with his former partner Courteney Cox.
The video showed the couple’s three-year-old son Charlie holding the baby scan and saying: “Baby!”
“So incredibly blessed and honoured that my wife @christinaarquette is pregnant with a baby boy,” Arquette wrote.
“Charlie and Coco are so excited and I am over the moon!”
Arquette and married Christina in April 2015, having welcomed their son Charlie two years earlier.
The actor has previously opened up how having his second child gave him a new appreciation for fatherhood.
“Since Charlie has come into my life, I love Coco more than ever,” he told PEOPLE in 2014.
“Having a son has brought back memories and made me realise how much I miss enjoying her as a baby.
“I am older and more mature and can return to raising a baby more aware of the wonderful daily experiences.”