The 2017–18 season saw Thatcham win the FA Vase, beating the club's previous best performance in the competition. On 21 October, they started in the first round of the competition defeating Horsham YMCA 2–1 at Waterside Park, before an 8–2 victory over Broadbridge Heath in the next round on 11 November. The third round saw Sevenoaks Town fall 3–1 on 2 December, while, on 6 January, Biggleswade were dispatched 2–1 in the fourth round. A 2–1 victory against Bromsgrove Sporting on 3 February saw the club reach the quarter-finals, equalling the club's record performance in the competition set in 1989. On 24 February, a 1–0 victory away at Melksham Town put the Kingfishers into the semi-finals. On 17 March, they beat 1874 Northwich in the first leg of the semi-final 1–0, following a fourth minute penalty from Ross Cook in front of 1,134 at Waterside Park. The Kingfishers won the second leg 3–2, with a brace from Gavin James and a goal from Shane Cooper-Clark, to give them a 4–2 aggregate victory and a place in the final at Wembley Stadium. In the same season, Thatcham won the Hellenic Premier Division by +2 goal difference to earn promotion to the Southern League Division One.