Network Rail said services were suspended for a short time following the incident at Ingatestone, Essex at about 2pm.
An ambulance service spokeswoman said it was thought the men had suffered a 15ft fall from a crane.
She said their injuries were "potentially serious".
A Network Rail spokesman said: "Work to repair the overhead lines at Ingatestone has been suspended following an incident at the site.
"Three engineers have been injured and have been taken to hospital. The incident occurred shortly before 2pm."
An investigation has been launched.