The club won the Thurlow Nunn League Premier Division last season, and added the League Cup to complete a double, and will now be playing in the Bostik League (formerly Ryman League) this season.
They join fellow Suffolk sides AFC Sudbury, who were relegated after just one season in the Premier Division, and Bury Town in Division One North.
Their elevation brings the total to six the number of clubs – Leiston, Lowestoft Town and Needham Market are all in the Premier Division – from Suffolk playing in the upper echelons of non-league football.
Mildenhall Manager Dean Greygoose, who played for several Football League clubs, most notably 205 games for Crewe Alexandra, before enjoying spells at AFC Sudbury and Bury Town, said the club are looking forward to the next chapter in their history.
The 52-year-old said: “There has been a lot going on behind-the-scenes and a real determination to make sure we are ready. The supporters have been looking forward to this day for a few years now – it has been like waiting for Christmas.
“We are really excited. Since last Christmas when we were top and on course to win the league and promotion we have been looking forward to this day.
“We are also nervous as it is a new venture. We have brought in several new players so we will have to see how well they gel together.”
Mildenhall start life in the Bostik League away to Essex opponents Heybridge Swifts on Saturday, kick-off 3pm.
Greygoose (pictured above) admitted: “It would probably have been better for the boys and fans to be at home in our first game.
“It is a potentially difficult game to start the season, but I am sure the boys will be up for it. We have had a decent pre-season and a good week’s training.”
Following Saturday’s opener, Mildenhall entertain Norfolk side Dereham Town in their first home league game under the lights at Recreation Way on Tuesday, kick-off 7.45pm.
Greygoose said: “Tuesday nights tend to be special nights at Mildenhall and I know the boys are very excited about it. The pitch is in excellent condition and we are hoping to get a good crowd.”
After their opening two league games Mildenhall then face a tricky trip to Framlingham Town in the FA Cup Preliminary Round on Saturday, August 19th.
Framlingham set up the all-Suffolk tie thanks to their 3-1 victory over Wadham Lodge in a replay at Aveley FC, following a 0-0 draw at Badingham Road four days earlier.
The Castlemen, who play in Thurlow Nunn League Division One – two steps below Mildenhall – are experiencing the magic of the FA Cup for the first time in their 130-year history.
Greygoose said: “It is an exciting time for them. As we all know the FA Cup is a great leveller and they will be confident after winning their replay.
“They have got some good players, so we will be treating the game seriously and have already gathered information on them.”
Updated 09:15 - 12 Aug 2017 by Courtney Pettifor