Darren Foy, 40, from Southampton, his wife Sandra and their two children, missed the explosions by just half an hour after he finished the Boston Marathon in three and a half hours.
The chartered surveyor, who is chairman of the Lordshill Road Runners in Southampton and was competing in his fourth marathon, said: "There are reports here that the explosions came from a hotel at the finish line and I walked past there a few days ago to pick up my race number.
"It's such a soft target. There are hundreds of thousands spectators on the streets and 27,000 runners, so we got off lightly."
More top news
Philippa has the latest weekend weather for the east
Philippa has the latest weekend weather for the west
Saturday's weather for the east with Philippa