A 46-year-old man and a 38-year-old woman were arrested on Monday morning at an address in Romford, east London.
They were both arrested on suspicion of arson and taken to a police station in the capital, where they remain in custody.
The arrests are part of an ongoing probe into the attack on a memorial wall in Limes Avenue at around 12.15am on 27 April.
The wall contained pictures of protesters allegedly killed by the Iranian state in January, following a wave of protests across the country.
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Commander Helen Flanagan, Head of Counter Terror Policing London, said: “We are committed to protecting vulnerable communities in the capital.
“Detectives have been conducting extensive inquiries since this incident was reported to us last week and these two arrests are the result of that hard work.”
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