The man, aged in his early 40s, was arrested on Wednesday, 3 November on suspicion of racially aggravated criminal damage. He has been sectioned under the Mental Health Act and remains in the care of medical professionals.
At this time police are not looking for anyone else in connection with this investigation.
At 7.40pm on Saturday, 30 October police were alerted to reports of a male spraying swastikas on walls in the vicinity of a synagogue in Belsize Square.
Officers established that other swastikas had been sprayed on walls elsewhere in the surrounding area.
A 16-year-old male who was arrested later that day (30 October) on suspicion of religiously aggravated criminal damage has been released and told that no further action will be taken.
Detectives continue to work close with the local authority and communities within Belsize Park.