The 30-year-old NSW powerhouse had surgery last year but all rehabilitation attempts have not been able to get him to a point where he can play NRL again.
He fronted a media conference on Monday afternoon to formally announce the news.
"The shoulder is just not holding up. We tried our best to do full contact but I would have become a liability," Saifiti said.
"It would have been unfair on me and the team if I had tried to keep going.
"If I risked any more damage it would have affected my quality of life after footy with two young kids, and I want to have more with my beautiful partner. It would have been selfish for me to keep going."
Saifiti's last game for the Dolphins was in round eight in 2025 against Canberra, where his last act on a football field was scoring a rampaging try.
He had a shoulder reconstruction early in his career and a cleanout in 2023. The latest injury was the final straw.
"When the surgeon went inside he said it was one of the worst he had seen. I did a fair bit of damage to it scoring that try against the Raiders," he said.
Saifiti will be paid out the final two years of his contract, which ends in 2027. He said he would sit down with CEO Terry Reader to discuss a path post-footy.
Telling his teammates on Monday morning was tough.
"It was pretty emotional. I love those boys," Saifiti said.
"I've only got to play eight games with them but it was the best decision I ever made coming up here. I made friendships for life.
"Knowing how good this team can be, I think I could add something to it at my best. That is the thing that hurts the most."
Saifiti was the club's best player in his short stint after signing in 2025 after playing 183 NRL games for Newcastle, most of them alongside his twin brother Jacob.
"That is probably my proudest achievement. We were born on the same day and played in the backyard," he said.
"Me and Jacob debuted together as 19-year-old kids and that whole year we only won one game. I was still enjoying my footy, playing with and against my idols.
"It was tough. They are real loyal in Newcastle. We were getting 16 or 17 thousand (to games) and getting beaten by 60 every week. They are memories I look back on fondly.
"My kids were born there, I met my partner there and grew up down the road."
Saifiti represented NSW in seven State of Origin matches and was a key member of the successful sides that won the 2019 and 2021 series.
A proud Fijian, he also represented the Bati in three Tests.
"I got to live out my childhood dream and accomplish a lot of things," he said.
"If I walk away from a career and the only thing I get is a sore shoulder ... there are a lot of people doing it tougher than me."
Dolphins hooker Jeremy Marshall-King, meantime, is set to return for his first NRL game of the season against Canterbury on Thursday night after recovering from a knee injury.
He is likely to share the hooking duties with in-form utility Max Plath.
The Dolphins also welcome back five-eighth Kodi Nikorima from suspension.
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