A judge previously warned the former Olympian he would be jailed if he drove while disqualified.
Dennis, 36, was given a suspended 17-month jail term and banned from driving for five years in 2025 after pleading guilty to a charge of committing an aggravated act likely to cause harm.
Ms Hoskins, 32, was struck by her husband's vehicle near their home at Medindie, in Adelaide's inner north, on December 30, 2023.
She suffered serious injuries and died in Royal Adelaide Hospital.
On June 11, the father-of-two was reported for driving while disqualified and his car was impounded for 28 days after police allegedly observed him driving with two children as passengers.
On Friday, Dennis pleaded guilty to the charge when he appeared in Adelaide Magistrates Court.
The case was elevated to the District Court, where he will face sentencing on September 4.
The court is also expected to deal with his breach of a good behaviour bond.
At sentencing in May 2025, Dennis had agreed to the $100, two-year good behaviour bond and his driver's licence was suspended for five years.
Judge Ian Press warned him any violation of the driving suspension would be a breach of the bond and Dennis would be jailed.
In March, Dennis was criticised over an Instagram post in which he shared a photo of a black Porsche with the caption: "What an absolute weapon".
SA Victims Rights Commissioner Sarah Quick said the post was "deeply offensive" and demonstrated "a clear lack of insight into the real and lasting impact of the harm he has caused".
"It also reflects a profound lack of respect for Melissa and her family," she said.
After sentencing in May 2025, Ms Hoskins' father Peter Hoskins said the family had not yet received an apology from Dennis, "but I'm sure that will come in time".
"There are two young children caught up in this tragedy … who have lost their mum, for them to then go and lose their dad … I don't think that (a jail term) would be ideal at all," he said.
"From the outset it (a jail term) wasn't something we were pursuing."
Ms Hoskins competed at the 2012 and 2016 Olympics on the track in the team pursuit and won the world title in that discipline in 2015.
Dennis won two world titles in the road time trial, as well as silver in the team pursuit at the 2012 Olympics and bronze in the road time trial at the Tokyo Olympics.
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