"Do not 'dumb walk', which is walking and texting or playing Pokemon Go - keep your head up," the memo said.
Staff were encouraged to "buddy up" while in public to watch each other's back, to not walk with hands in pockets and were reminded of "stranger danger".
"Turn and go in the opposite direction if a stranger in a car offers you a ride."
The Defence Force memo warned staff against complacency.
"The worst thing you and I can do from now on is assume that it won't happen to me. This normalcy bias is no longer appropriate when the definition of normal has changed for good and a false sense of security could in fact be deadly."
Jeffrey Sluka, a Massey University academic who specialises in political terrorism, described the security warning as "patently ridiculous and deranged".
"You can't live in fear and have eyes at the back of your head - a psychologist would call that a paranoid mental state," said Sluka.
"Any threats on our security forces were unlikely compared to London, which has a massive Muslim population and people being involved with militant Islamic groups. New Zealand doesn't have that."
Sluka acknowledged there were young men living in New Zealand who had been indoctrinated by Isis, but he still considered the memo to be over the top.
"It's irrational and dangerous to ramp up people's fears to see dangers where they don't exist."
A spokesman for the NZDF said the safety message to staff about personal security was not because of a specific threat.
"The NZDF's senior leadership is strongly committed to the duty of care they have for our people, and regularly communicates with staff as part of maintaining a high standard of security awareness and to remind them of basic precautions. [The memo] has been very positively received by staff."
Despite New Zealand's geographical isolation from hotspots in Europe, intelligence agencies treat terror-related incidents seriously. Passports have been seized from people planning to travel to Syria and up to 40 individuals are being actively monitored.
Recently, Imran Patel, a 26-year-old from Auckland, was jailed for three years after pleading guilty to possessing, making and distributing extremist video footage of people being beheaded and burned alive.
In a separate incident, an Isis sympathiser, Niroshan Nawarajan, was sentenced to five months on home detention for possessing extremist publications.
The 27-year-old was arrested after walking into the United States consulate in Auckland and asking if the building was "bomb-proof".
Security tips for NZ Defence staff
• Do not be easily distracted by using smart devices. Do not "dumb walk", which is walking and texting or playing Pokemon Go - keep your head up.
• If you can, buddy up when travelling - two sets of senses are better than one and each of you can watch the other's back.
• Always walk facing oncoming traffic. Remember the young soldier killed in London was hit from behind. So too were many in Nice, France, in the recent attack.
• Avoid passing stationary cars with their engines running and people sitting inside them.
• Turn and go in the opposite direction if a stranger in a car offers you a ride.
• Always remove your identification on exiting a Defence facility. Do it inside the building before you step outside.
• Avoid using isolated public transport stops - if you must use one, don't stand in one spot - move around.
• Keep both hands free when walking - don't walk with hands in your pockets for example.
• Do not get into a lift with another person if you don't like the look of that person - take another lift or if you must take the lift with the person, stand next to the control panel so as to be able to activate the alarm.
• Vary your personal routine. Avoid leaving the house at the same time each day. If you can, use different routes to travel to regularly visited places such as work.
• Be observant when using your car after it has been parked for any length of time - again a quick once-over will usually alert you to any tampering and you can do that covertly.
