Winning the Combined Counties League title resulted in Merstham being promoted to Division One South of the Isthmian League. In 2014–15 they finished fourth in the division, qualifying for the promotion play-offs. After beating Faversham Town 5–4 on penalties in the semi-finals, they defeated Folkestone Invicta 3–0 in the final to earn promotion to the Premier Division. They finished the season by winning the Surrey Senior Cup for a second time. In 2016–17 the club reached the first round of the FA Cup for the first time, losing 5–0 at home to Oxford United in front of a record crowd of 1,920. They won the Surrey Senior Cup again in 2017–18.