The actress decided to share an adorable photograph showing her hugging the birthday boy, which she captioned, "Moses Bruce Paltrow Martin turns 8 today. We love you!"
It is a very rare picture of Gwyneth's son, who like his sister Apple has been well shielded from the public eye.
Aside from a glimpse of her second child, the black and white snapshot also shows off the star's wedding ring which is clearly visible as she cradles her son's head.
It comes two weeks after Gwyneth and husband Chris Martin announced the end of their ten year marriage.
In a joint statement confirming the news, the couple said, "It is with hearts full of sadness that we have decided to separate.
"We have been working hard for well over a year, some of it together, some of it separated, to see what might have been possible between us, and we have come to the conclusion that while we love each other very much we will remain separate."
It went on: "We are, however, and always will be a family, and in many ways we are closer than we have ever been. We are parents first and foremost, to two incredibly wonderful children and we ask for their and our space and privacy to be respected at this difficult time.
"We have always conducted our relationship privately, and we hope that as we consciously uncouple and coparent, we will be able to continue in the same manner."
Gwyneth faced more heartache recently following the passing of her grandmother Dorothy Paltrow on 31 March. Dorothy was the mother of Gwyneth's father Bruce, who died in 2002 from cancer. The family are expected to hold a private memorial service in the near future.