"I put him on his back and started giving him CPR, and after a little while he took a big breath, so I put him back in recovery," he told Fairfax.
Mr van Velthooven was rushed to Wellington hospital and remained in an induced coma until Sunday.
His sister Claudia van Velthooven took to social media to find the men that saved her brother's life.
"On Friday night a tall, young guy collapsed on the street near tommy millions. Two guys rushed over and performed CPR while his friend called the ambulance.
"The guy who collapsed is my brother and I am trying to find these two guys as my family would like to thank you -- you saved my brother's life. If anyone knows who these two guys could be, can you please share/comment this post so that these guys can make themselves known to me. They are truly heroes," she wrote.
Mr Rudman was identified by his friends who saw the post and he met van Velthooven's family in hospital on Tuesday.
Claudia van Velthooven said Mr Rudman was a hero and his actions saved her brother's life.
"Hearing Isaac was on the ground with no pulse is quite hard, but the fact that Neil was there, and getting to meet him to thank him, he's a hero," Ms van Velthooven said.