Detectives said the device, if it had exploded, could have resulted in the death of the garda, members of his family or passersby.
The appeal was made on the same day as a bomb went off in a Wicklow village, seriously damaging two cars.
Gardaí are investigating if that attack is linked to a drugs dispute or a fight between two men which occurred last August.
In the Leitrim incident — which happened in April 2014 but only made public yesterday— an explosive device was found at the front door of a serving garda’s house in the Drumlish area.
The device was discovered in the middle of the day on April 17, 2014.
“We are appealing to anyone with information on this very serious matter to come forward,” said Detective Inspector James Delaney, who is leading the investigation.
“This was a viable improvised explosive device and could have resulted in death or serious injury to the residents of the house it was left outside, or members of the Drumlish community.”
He said gardaí were of the view that there were people who knew something about the incident.
“We believe there are persons out there that have information that would be beneficial to the case.
“Perhaps you were aware of suspicious activity in the run-up or on Thursday 17 April last year and thought nothing of it at the time.
“Even the smallest piece of information, which may seem insignificant, might help with the investigation.”
The appeal was made jointly with Crimestoppers. Det Insp Delaney said calls to Crimestoppers were anonymous and that callers can give information without needing to provide personal details.
People can receive an award for information which significantly assists the Garda investigation.
Crimestoppers can be contacted on 1800 250025.
Meanwhile, gardaí in Baltinglass are investigating an explosion in Dunlavin village in west Wicklow.
Gardaí were alerted by a resident in Church Hill estate at around 1am when the bomb went off under a car, seriously damaging it. A second car was also damaged.
Gardaí secured the area and alerted the Defence Forces and requested an army bomb disposal team.
The Defence Forces issued a statement saying that the Explosive Ordnance Disposal (EOD) Team was deployed “after an improvised explosive device detonated in a residential area”.
It said the EOD team arrived on the scene at 5.50am and conducted a search of the area and carried out a post blast analysis.
They declared the scene safe at 7am, which allowed gardaí to commence a technical examination.
Gardaí are investigating a possible cause for the attack and are examining local individuals and incidents that might be linked to it.
It is thought a drug dispute may be a factor, along with a fight between two men that occurred in the area in recent months.
Sources said the owner of the car targeted was not involved in the dispute.
Gardaí are appealing to anyone in the estate, or in Dunlavin, who saw anything suspicious to ring Baltinglass Station 059 6482610.
Local Deputy Billy Timmins, Renua, said the attack was a “worrying development” and “fortunately no one was injured”. He called on anyone with information to contact gardaí.