The body of 25-year-old Aaron Armstrong was discovered at a property in Blyth, Northumberland, on Tuesday afternoon.
Northumbria Police – which did not name Armstrong – told Sky News there was not believed to be “any third party involvement” and a report will be prepared for the coroner.
In an emotional tribute to Gradon shortly before his death, Armstrong said: “I will see you very soon my angel so keep our bed warm for me.”
He had also shared an image of the order of service from her funeral, writing: “I love you with all my heart my beautiful angel.
“I’m absolutely heartbroken, I can’t stop crying and I can feel your spirit in my soul. RIP Sophie Hannah Gradon.”
TV personality Gradon died on 20 June at the age of 32.
Police said there were not believed to be any suspicious circumstances surrounding her death.
At the time, Armstrong said he was “absolutely devastated” and posted a picture of the pair together on Facebook.
“I will never forget that smile I love you so so much baby your my world forever ever and always,” he wrote.
Armstrong joined Gradon’s co-stars from the 2016 series of Love Island at her funeral last Thursday.
Zara Holland, who also appeared on the ITV2 dating show, posted an emotional tribute on Instagram, saying it was a “beautiful private service”.
Gradon, from Newcastle, was one half of Love Island’s first same-sex couple and had been crowned Miss Great Britain in 2009.
She and Armstrong had recently returned from a holiday in the resort town of Antibes near Cannes and Nice in southern France after celebrating his birthday.
The day before she died, Gradon posted a video on social media of her boyfriend dancing with a dog, describing her other half as the love of her life and “the one”.
Just days earlier she had paid tribute to nightclub boss Paul Burns, who had died at the aged of 37.
Gradon’s parents, Colin and Deborah, paid tribute to her following her death, calling her a “precious daughter”.
“We as a family are still coming to terms with our sudden loss. Our hearts are broken,” they said.
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