Hemmings netted in each half as Harriers beat Brackley Town 2-0 in the National League North play-off final.
It was their ninth win on the spin and completed a remarkable turnaround for a team which sat in the bottom half of the table as recently as April 1.
Hemmings, who came through the youth ranks at Wolves and made his debut in the 2009 Championship-winning campaign, has been a mainstay of the starting XI since arriving at Aggborough in 2019.
He said: “This means everything. This is my first medal. Years ago I played for Wolves when they won promotion from the Championship but I don’t count that, as I only played two games.
“This is the one I am going to treasure for the rest of my life.
“This is my proudest moment. I came to Kiddy in 2019 and wanted to push this team to the next level.
“Now we have done it I can’t wait to play at the higher level. From day one they have supported me, believed in me and got the best out of me.”
Hemmings credited team spirit with helping Harriers surge to promotion at the end of an often difficult season.
Their nine-match winning run was preceded by nine games without a win which placed boss Russ Penn and assistant Jimmy O’Connor under considerable scrutiny.
Hemmings said: “Promotion was the aim at the start of the season. I know we had a poor start but the last few months have been amazing.
“Team spirit, you know, has just pushed and pushed us. This is a great day. This is what we wanted.
“Nine matches on the bounce? No-one would have thought we could do that but we stuck together and that is what saw us through. This is the success we have.
“We expected to be up there at the start of the season. It was Russ and Jimmy’s first experience of going through the rough times but they learned a lot, we learned a lot and the most important thing is we stuck together.”
Hemmings pounced on a defensive mix-up to fire Harriers in front after just 12 minutes before netting an excellent second on the hour mark.
He said: “Sometimes you want to score a worldie but on a day like this you don’t mind how you go in.
“Whoever scores first has the upper hand. We defended great as a team.”