Founded in 1924, Kelso play their home matches at Woodside Park on Drying House Lane. The first league the club played in was the Border Junior League. Their first notable success at this level was winning the Dudley Cup in 1935. The next season United joined the Berwickshire FA, despite being based in Roxburghshire. Season 1937-38 was very successful for the club, as the Conan Doyle Cup, the Dudley Cup and the league Championship Shield were all added to the Honours list.
Although no one from Kelso at that time became an internationalist, many went to bigger, professional clubs.
After the war Kelso United reformed and entered a 2nd XI into the Kelso and District League, while the main team played in the Border Amateur league. In 1957-58 the club lifted the South of Scotland Cup East section, but lost the overall final to West section winners Broughton.
Season 1959/60 was another good year with the Border Cup and the Ancrum 5-a-side competition being annexed.
In the mid-sixties after a massive gap of 29 years, United were once again Border Amateur League champions. Big decisions were made leading up to 1967-68, one was that the first team would join the East of Scotland League and that the second team which had disappeared, would reform and take the first teams place in the Border League. This was a successful move as the United team were League and King Cup runners-up. In 1971 the club decided to work more on bringing in local players, but this was not sustainable and they left the East of Scotland League. However, back in the Amateur League the club flourished, conquering the Beveridge Cup as well as the South of Scotland Cup. In 1974 they won the Border Cup.
By 1974-75 the club felt ready to rejoin the East of Scotland League, and in 1980 won their biggest cup yet, the King Cup. Since then the club have held their own in the league, reaching the final of the Image Printers Cup in the mid-nineties as well as getting promoted to the Premier league in 2004, although they were relegated at the end of season 2005-06
Kelso United play in the East of Scotland League Division 1, while Kelso Thistle play in the Border Amateur League.
Kelso Football Club compete as part of the Scottish Borders Junior FA with small-sided teams at Under 8, 9, 10, 11 and 12 and youth teams at Under 13, 14, 15 and 17.