Jury members in a "secret trial" being held at the Old Bailey were told that Blair's address was written on a piece of paper found in the accused British man's car.
An attack could have been planned on the Blairs
Erol Incedal is accused of planning acts of terrorism and possessing a "bomb making" document.
The 26-year old from London denies the charges.
His trial is partially held in secret, and parts of it will never become public.
Opening the trial, prosecutor Richard Whittam QC told jurors Incedal was stopped on 30 September 2013, for a road traffic offence.
Inside the car he was in - a black Mercedes - police found a piece of paper with the address of a property owned by the Blairs on it, inside Incedal's glasses case, the court was told.
A sketch of Incedal in court
Mr Whittam said: "Count 1 does not suggest that Erol Incedal had settled on a specific target or a particular methodology but in the context of the case as a whole and the evidence that I am going to come to, you may think that this address does have some significance."
During the search, a listening device was put in the car, the court was told.
Outlining the prosecution case, Whittam said: "You will hear that he was actively engaged with another or others who were abroad.
"The prosecution case is that such engagement was for an act or acts of terrorism either against a limited number of individuals, an individual of significance or a more wide-ranging and indiscriminate attack such as the one in Mumbai in 2008."
Other items seized from the car included an Acer computer and a Sim card and USB dongle.