The SDLP politician was sent a bullet and sympathy card on Wednesday morning.
It's the latest in a series of threats made to Mr McDevitt since December.
However the MLA said he will not be deterred from his work at Stormont.
"These threats only strengthen my determination that we must work towards a better future for everyone in this region, and will not prevent me from doing the job I have been democratically elected to do," Mr McDevitt insisted.
"The foundations for a new society laid by the Good Friday Agreement will never be undermined by those who seek to drag us back to violence."
South Belfast Alliance MLA, Anna Lo, condemned those responsible.
"I am disgusted that Conall has been targeted in this way," she said. "There can be absolutely no justification for this or any other death threat.
"The targeting of politicians in recent months is an attack on democracy."
Meanwhile a statement from the Policing Board said: "We know that this threat will not deter Conall from his work on behalf of the community but it is nonetheless deeply disturbing that this threat was sent. Our thoughts and support are with Conall and his family at this time."