The 20-year-old man was detained over the death of a man in his 40s near the Wellington monument in the early hours of Friday.
He was taken in for questioning to Finglas Garda station where a 27-year-old man arrested yesterday was also being held.
Detectives believe the dead man was violently beaten before being set alight in a sleeping bag.
Archbishop of Dublin Diarmuid Martin addressed the killing in a homily yesterday and said he is horrified by it.
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