A father has got a tattoo to match a scar left on his son's head after cancer surgery.

Josh Marshall's eight-year-old son Gabriel was diagnosed with a rare form of brain cancer called anaplastic astrocytoma in March 2015.

Mr Marshall said surgeries to remove his son's tumour left him bald with a scar on the right side of his head.

"My son was very self-conscious after he got his surgery - he felt like a monster," Mr Marshall told ABC News.

The father then decided to get a tattoo mimicking his son's scar in effort to make him fell less insecure.

"I said, 'You know what, I'll get your scar tattooed'," Mr Marshall said. "'That way, if people want to stare at you, then they can stare at both of us'."

Gabriel loves his father's tattoo and tells people that he and his father are like twins.

Mr Marshall and his son won the St. Baldrick Foundation's #BestBaldDad competition, beating 54 other dads who shaved their heads in solidarity with their children who have cancer.

The photo of the father and son received more than 5,000 votes.

He told ABC News that Gabriel is doing well, and although a small portion of the tumour remains, it has not grown. He receives a scan once every three months.