Brandon Yates, 28, was fatally wounded on August 17 in Wollongong, south of Sydney, but authorities did not make any arrests over the incident until Wednesday morning.
Officers had been told Mr Yates left a unit on Crown Street, but returned a short time later with a stab wound before eventually collapsing.
He was treated by paramedics and transferred between multiple hospitals in an attempt to treat stab wounds to his chest, but he died six days later.
On Wednesday morning, police announced they had executed a search warrant at an address in Wollongong and arrested a 41-year-old man.
He was taken to a nearby police station, but has not yet been charged.
Detective Acting Superintendent Glen Broadhead said the man arrested knew the victim but would not provide further details about their relationship.
He said the alleged offender was known to police and that further arrests would be coming in the course of the investigation.
"There are a number of people who we believe will be arrested in relation to various offences - one in particular which will relate to the (stabbing) incident," he told reporters.
Appealing for answers over her brother's death in November, Shantelle Yates revealed the pain she felt losing the "cheekiest, most mischievous person''.
"(It was) totally devastating, waking up and getting that phone call, getting to the hospital, just seeing him pretty much gone in a coma, knowing someone would take my brother's life for nothing,'' she said.
"Switching off his life support, having to watch my brother pass away, because someone wanted to take his life, I now have to pay the consequence of losing my brother, losing my best mate."
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