Keaton Critchell was instrumental with the bat, scoring 51 as his side could only manage 162.
Christiaan Moir scored 28 to propel Midland-Guildford to the par score. Captain Stewart Walters ripped through the bottom order to give his side an unlikely victory. Will Riley was also impressive with two wickets, in rounding out a decent season for Midland-Guildford.
The result means the Swans finish the 2015-16 season in 8th spot, 10 points outside the top six.