Police said the incident happened Monday. The dog, named Tinsley, was seen running on the Memorial Bridge on I-89 from Lebanon to White River Junction. Officers, thinking the dog was lost, tried to catch it.
Instead, Tinsley led officers to a guardrail where a pickup truck had rolled over and crashed.
"They discovered a truck which had been overturned with two gentlemen that were ejected from the vehicle," said Lt. Daniel Baldassarre, New Hampshire State Police.
Both people inside the truck, including Tinsley's owner, were hurt but are expected to be OK.
CNN contributed to this report