Their fire truck hit a fallen tree.
The bravery award was presented to young Harvey Keaton by New South Wales Fire Commissioner Shane Fitzsimmons.
Australian Prime Minister Scott Morrison also attended the funeral.
Morrison said he was there to "remember and give thanks for the life and service of Geoff Keaton".
The NSW Rural Fire Service released photos of the ceremony, showing the toddler being held by his mother as they look at the coffin.
A mug with the message "Daddy, I love you to the moon and back!" rested next to the coffin.
Another firefighter died on Monday when high winds overturned his truck.
Since September, 18 people have died as a result of the fires. A number of people remain missing.