Jonathan Wilson, 33, of Woodthorpe Avenue, Boston, pleaded guilty to to the manslaughter of James “Jimmy” Britton on the grounds of diminished responsibility when he appeared at Lincoln Crown Court.
He also pleaded guilty to section 18 grievous bodily harm against another man, and not guilty to the robbery of a van.
It was agreed the charge of robbery of the van will sit on file.
The prosecution were represented by Katherine Goddard QC.
Wilson, who was due to stand trial in September, was remanded back into custody by Judge Simon Hirst and will now be sentenced at Lincoln Crown Court on 19 July.
Lincolnshire Police launched an investigation after officers, along with other emergency services, attended the report of a collision in Everingtons Lane, Skegness, at 4.14pm on Wednesday November 19.
The collision was between a Ford Transit Van and two pedestrians, one man aged 20 and another man aged 37. The 20-year-old man suffered serious injuries, not believed to be life threatening.
Sadly, the 37-year-old man, James, known affectionately as Jimmy, Britton, from Skegness, died in hospital on November 18 as a result of his injuries.
A former student at Haven High Academy in Boston, many tributes were paid to Mr Britton as "a wonderful son" and father of twins on social media.
Peter Lindsay said: "Jimmy Britton was such a big softy and I had the pleasure of meeting him when I first opened 100% gym,
"I trained him on and of for about two or three years before he moved away from town.
"We always had such a great laugh in the gym and soon became good friends.
"You made a lot of people laugh and smile bro and we will still laugh at the good times we have all had with you. Rest in peace up there bro."
George Gray said: "Rest easy Jimmy. See you on the other day - you definitely will be missed by hundreds of people."
Jane Moody Beachus said: "RIP Jimmy. A lovely man a wonderful dad and a fantastic son. Thinking of you all at this sad time."