The former Black Eyed Peas singer captioned the shot "Axl Jack Duhamel. Day 2 of life. Hearing test complete. All systems go. #chillin."
Her hubby Josh also posted another pic on his own Instagram, captioning the shot, "Axl Jack Duhamel Day 1 Life is good :) #paparazziyoucanleaveourhousenow."
Fergie gave birth to the baby boy on August 29 in L.A.
The couple married back on January 10, 2009.
The Black Eyed Peas have been on hiatus since 2011.