The news was shared on Instagram when photos from Harding's recent baby shower were posted online.
It was first confirmed that the pair were expecting in October 2014.
A spokesman for Law said: "I can confirm that Jude Law and Catherine Harding are expecting a child together in the spring. Whilst they are no longer in a relationship, they are both wholeheartedly committed to raising their child."
This baby will be the fifth child for the 42-year-old actor, who has two sons and a daughter with his ex-wife Sadie Frost, and a daughter with previous girlfriend Samantha Burke.