Kyan Hotchkiss took part in a Race for Life event at his school, Meadows Primary School, in Ketley, to raise money for charity.
He acted after his beloved nan Jayne was diagnosed with multiple myeloma.
Kyan ran 3km, wearing a shirt with Jayne's picture on, and has now collected more than £1,000 to help find a cancer cure.
Proud mother Steph said: "Kyan and his nanny are inseparable and he struggled when he heard of her diagnosis.
"He wanted to take part in the event for his nan and was determined to raise money to help people. His aim was £250, so to make more than £1,000 is incredible.
"It was so emotional watching him run. His dad, Rob (Jayne's son) said it melted his heart.
"It's amazing what he has done and we, as a family, are just so incredibly proud of our boy."