In the semi-final, the Swifts beat Durhamtown Rangers, who then protested on the basis that Mossend was not actually in Linlithgowshire, and so the club should not be allowed to enter.

Mossend pointed out that it had been invited to join the association and paid its scrip; the Rangers produced a letter from Lord Rosebery setting out the terms of the competition, namely it was for clubs in the county only.

Its first season as a senior club saw it win the King Cup (for members of the East of Scotland FA), beating Burntisland Thistle 4–1 in the final; the club went behind in the first five minutes, but goals from Howieson, Boyd, and Ellis put the Swifts 3–1 up at the break, and the Swifts employed a tactical change - Howieson stepping back to midfield, to make two banks of four in front of the full-backs - to preserve the lead.

[7] The club's best run in the national competition came in 1888–89, reaching the final 16; in the first round the Swifts caused a major shock by defeating Hibernian 2–1at Mossend Park in front of a crowd of 2,000.

The Swifts protested its defeat in the re-played tie on the grounds of roughness on the part of Dumbarton, but to no avail; although the referee reported Dumbarton's Madden to the Scottish FA for repeated tripping, he also reported the Swifts' Ellis and Mackay for kicking their opponents in the stomach, Mackay kicking Stewart so hard that Stewart was knocked unconscious for an hour.

[13] The Shield was a different matter, the Swifts apparently losing 2–1 at Tynecastle Park, but a protest that Vale's left-back Oag and inside-right Phillips for "professional irregularities" was upheld.