The Metropolitan Police said the men, aged 45 and 47, were arrested in London on suspicion of arson with intent to endanger life, and were taken to a police station for questioning.
Commander Helen Flanagan, head of Counter Terrorism Policing London, said the arrests marked "an important breakthrough in the investigation".
But she noted that surveillance camera video of the incident suggested three people were involved.
Police have not declared the incident to be a terrorist attack, but are investigating a claim of responsibility by a group with potential links to Iran.
The blaze early on Monday morning in Golders Green, a London neighbourhood with a large Jewish population, consumed four ambulances belonging to the volunteer organisation Hatzola Northwest.
Oxygen cylinders on the vehicles exploded, breaking windows in an adjacent apartment block.
Also shattered was the community's shaky sense of security, already strained by wars in the Middle East and what many say is soaring hatred of Jews.
The UK has accused Iran of using criminal proxies to conduct attacks on European soil targeting opposition media outlets and the Jewish community.
Britain's MI5 domestic intelligence service says more than 20 "potentially lethal" Iran-backed plots were disrupted in the year to October.
Police are probing a claim of responsibility posted on social media by a group calling itself Harakat Ashab al-Yamin al-Islamia, which translates as the Islamic Movement of the Companions of the Right.
Israel's government has described it as a recently founded group with suspected links to pro-Iran networks that has also claimed responsibility for synagogue attacks in Belgium and the Netherlands.
Metropolitan Police chief Mark Rowley said detectives were investigating the claim but it was too early to attribute the attack to the Iranian state.
