A video taken before Saturday night's pre-season friendly between Manchester City and AC Milan has gone viral.
City manager Guardiola appeared to seek out Ibrahimovic, who now works as an advisor for Milan's owners, before they shook hands.
Ibrahimovic later shared the clip via his Instagram account alongside the caption: 'Just a friendly game'.
However, the relationship between Guardiola and Ibrahimovic has been famously unfriendly in recent years.
Striker Zlatan Ibrahimovic pictured (left) speaking with manager Pep Guardiola (right) during a UEFA Champions League semi-final game between Barcelona and Inter Milan in April 2010
Guardiola was Ibrahimovic's manager at Barca in the 2009-10 season.
Barca won four trophies that season - La Liga, the Supercopa de Espana, the UEFA Super Cup and the FIFA Club World Cup - and Ibrahimovic contributed 21 goals.
But he and Guardiola were not on the best of terms.
Ibrahimovic later slammed Guardiola in his 2013 autobiography I Am Zlatan, calling him a 'spineless coward'.
The book also saw Ibrahimovic reveal that he had told Guardiola to 'go to hell' and that he did not have 'any balls' during Barca's Champions League semi-final defeat by Inter Milan in April 2010.
Despite their previous bad blood, Guardiola and Ibrahimovic shared a handshake, a hug and a very brief chat at the weekend.
Reacting to the video, one viewer tweeted: 'Zlatan and Pep looking like awkward exes meeting each other for the first time after a bad breakup'.
One cCity supporter then wrote: 'Look how Zlatan can't keep eye contact. He's the same guy that called Pep a coward, how ironic.'
A second City fan added: 'Zlatan cannot even look Pep in the eyes after years of slandering him,' followed by a clown emoji.
Another tweet read: 'Wow Zlatan HATES Pep. And Pep knows it. What a masterclass in human interaction s***housery.'
City lost 3-2 to Milan in New York, having started their pre-season tour of the States by being beaten 4-3 by Celtic in North Carolina.
City will be hoping to record their first win of the summer on Tuesday night when they take on Barcelona in Orlando.