Bruce Baker had returned from shopping with three of his children when the potentially deadly discovery was made.
The snake was motionless at his front doorstep - a short distance away from his one-year-old daughter - until the car technician gave it a little kick.
It then moved so he got help from a neighbour to coax it into a plastic box until the Scottish SPCA arrived at his home in the Scottish Borders.
The father-of-four, from Innerleithen, said: “I was shocked, it’s about 7ft - this thing is massive.
“It’s not something you expect to see on your doorstep.
“The kids were totally fine, blase. The older ones wanted to go and touch it.
“You play it back in your head, what could have happened.”
He added: “It’s one that can wrap around you, it has so much power, it’s just one big muscle.
“It was quite scary but nothing happened.”
The boa constrictor was found in his front garden on Sunday and is believed to be a lost pet.
Mr Baker, 32, managed to contain the non-venomous snake and phoned the Scottish SPCA animal helpline.
Scottish SPCA animal rescue officer Jamie Cameron said, “I attended a property in Innerleithen on April 21 after a caller reported a stray snake.
“The snake was an approximately 7ft-long boa constrictor and has been taken to our animal rescue and rehoming centre in Edinburgh.
“He is quite thin so we believe he has been straying for some time.”